[Technical Field]
[0001] The present invention relates to a polishing composition used for polishing a polishing
object. In particular, it relates to a polishing composition used primarily for polishing
semiconductor substrates such as silicon wafers as well as other substrates.
[Background Art]
[0003] The surface of a silicon wafer used as a component of a semiconductor device, is
generally polished to a high quality mirror finished via a lapping step (rough polishing
step) and a polishing step (precision polishing step). The polishing step typically
comprises a first polishing step and a final polishing step. Patent Documents 1 to
3 are cited as technical literatures related to polishing compositions used primarily
for polishing semiconductor substrates such as silicon wafers.
[Citation List]
[Patent Literature]
[0004]
[Patent Document 1] Japanese Patent Application Publication No. 2005-085858
[Patent Document 2] Japanese Patent Application Publication No. 2004-128070
[Patent Document 3] Japanese Patent Application Publication No. 2010-034509
[Summary of Invention]
[Technical Problem]
[0005] Lately, higher quality surfaces have been demanded in semiconductor substrates such
as silicon wafers. The precision of substrate surface inspection has also been improved.
For instance, surface analyzers have been developed to detect fine defects such as
scratches and bumps, that are several deca-nanometers deep or high. If fine defects
such as those detectable by these systems can be reduced, surfaces of higher quality
can be obtained.
[0006] Patent Document 1 discloses a technique that uses a polishing compound comprising
hydroxyethyl cellulose and/or polyvinyl alcohol as well as a block polyether to improve
the haze of a silicon wafer. Patent Document 2 discloses a technique that uses a polishing
composition comprising colloidal or fumed silica having an average primary particle
diameter of 5 nm to 30 nm and a water-soluble polymer to reduce the surface haze of
a semiconductor wafer. However, haze reduction alone cannot effectively reduce fine
defects (micro defects) as described above. Patent Document 3 teaches a technique
that uses a water-soluble polymer having low viscosity as a semiconductor-wetting
agent to enable easy removal by filtration of contaminants capable of causing micro
defects and thereby to reduce the occurrence of micro defects. However, such a technique
has been often insufficient in terms of the required level of latest micro defect
reduction.
[0007] US 2006/113283 (A1) discloses a polishing composition containing at least one or more aminocarboxylic
acids selected from the group consisting of serine, cysteine and dihydroxyethylglycine,
ceria particles and an aqueous medium; a polishing process of a semiconductor substrate,
including the step of polishing a semiconductor substrate with a polishing composition
for a semiconductor substrate, containing at least one or more aminocarboxylic acids
selected from the group consisting of serine, cysteine and dihydroxyethylglycine,
ceria particles and an aqueous medium; a method for manufacturing a semiconductor
device including the step of polishing a semiconductor substrate having a film formed
on its surface, the film containing a silicon atom and having a shape with dents and
projections, with a polishing pad pressed against a semiconductor substrate at a polishing
load of from 5 to 100 kPa in the presence of a polishing composition for a semiconductor
substrate, containing at least one or more aminocarboxylic acids selected from the
group consisting of serine, cysteine and dihydroxyethylglycine, ceria particles and
an aqueous medium.
[0008] EP 1 813 656 (A2) discloses a metal polishing liquid comprising an oxidizing agent and colloidal silica
in which a part of a surface of the colloidal silica is covered with aluminum atoms,
and a Chemical Mechanical Polishing method using the same. An amino acid, a compound
having an isothiazoline-3-one skeleton, an organic acid, a passivated film forming
agent, a cationic surfactant, a nonionic surfactant, and a water-soluble polymer may
be contained. A metal polishing liquid which is used in Chemical Mechanical Polishing
in manufacturing of a semiconductor device, attains low dishing of a subject to be
polished, and can perform polishing excellent in in-plane uniformity of a surface
to be polished.
[0009] US 2011/183581 (A1) discloses a polishing composition, containing abrasive grains and an acid represented
either by R2-R1-SO3H (wherein R1 is a linear alkylene or hydroxyalkylene group having
1 to 4 carbon atoms, and R2 is a hydroxy group, a carboxy group, or a sulfonic acid
group when R1 is the linear alkylene group, or R2 is a carboxy group or a hydroxymethyl
group when R1 is the linear hydroxyalkylene group), or by C6H5-R3 (wherein R3 is a
sulfonic acid group or a phosphonic acid group). The acid contained in the polishing
composition is preferably isethionic acid or benzenesulfonic acid. The polishing composition
is mainly used in the application of polishing silicon oxide materials including glass
substrates for hard disks, synthetic quartz substrates for photomasks, and low-dielectric-constant
films such as silicon dioxide films, BPSG films, PSG films, FSG films, and organosiloxane
films of semiconductor devices.
[0010] An objective of the present invention is thus to provide a polishing composition
that allows reducing the number of detectable micro defects as described above in
a surface after polishing therewith. Another objective of this invention is to provide
a method for producing such a polishing composition. Another related objective is
to provide a method for producing a polished article (e.g. substrate) comprising a
surface having few micro defects.
[Solution to Problem]
[0011] When a polishing object (work piece) is polished with a polishing composition comprising
an abrasive and a water-soluble polymer in water, depending on the type of water-soluble
polymer, the water-soluble polymer may adhere to the abrasive in the polishing composition,
causing the abrasive to exist in the polishing composition as aggregates dimensionally
larger than the abrasive itself (abrasive grains alone). Such aggregates may behave
as grains in the polishing composition and their behavior may affect the mechanical
working during the polishing. With respect to a polishing composition comprising an
abrasive and a water-soluble polymer in water, as a physical value different from
the dimensions of the abrasive itself, the present inventors have focused attention
on the grain size in consideration of the presence of the aggregates. In other words,
when the water-soluble polymer adheres to the abrasive (abrasive grains), entities
that exhibit particle-like behavior in the polishing composition have been perceived
as grains and their size has been considered as the size of the grains in the polishing
composition. Using dynamic light scattering as the means capable of accurately determining
the grain size, earnest studies have been conducted on the relationship between the
grain size and micro defects in polished surfaces. As a result, grain sizes capable
of effectively reducing the micro defects have been discovered, whereby the present
invention has been completed.
[0012] The polishing composition provided by this invention comprises an abrasive, a water-soluble
polymer, and water. The polishing composition has a volume average particle diameter
D
A of grains (which can be the abrasive alone, abrasive with surrounding water-soluble
polymer adhered thereto, abrasive/water-soluble polymer assemblies) in the polishing
composition of 20 nm to 60 nm when measured by dynamic light scattering at a concentration
equivalent to 0.2 % (by mass) abrasive content. In addition, the abrasive contains
a silica grain and has an average secondary particle diameter D
P2 of 20 nm to 60 nm, and the polishing composition has a pH of 9.0 to 11.0. According
to such a polishing composition, because the volume average particle diameter D
A of the grains is limited to the prescribed range, the occurrence of micro defects
(in particular, surface defects caused by polishing processes, generally called PID
(polishing induced defects) can be effectively reduced.
[0013] A preferable abrasive has an average primary particle diameter D
P1 in a range of about 15 nm to 30 nm. A polishing composition comprising such an abrasive
can achieve both reduction of micro defects and reduction of haze at a higher level.
[0014] A preferable abrasive has an average secondary particle diameter D
P2 in a range of about 20 nm to 50 nm. A polishing composition comprising such an abrasive
can achieve both reduction of micro defects and reduction of haze at a higher level.
[0015] A preferable water-soluble polymer has a weight average molecular weight (Mw) of
80 × 10
4 or less (e.g. 1 × 10
3 to 80 × 10
4, typically 1 × 10
4 to 80 × 10
4). A water-soluble polymer having such a Mw is preferable because it is suitable for
forming grains having a preferable volume average particle diameter D
A disclosed herein.
[0016] The polishing composition disclosed herein can be preferably made in an embodiment
further comprising a basic compound, in addition to the abrasive, water-soluble polymer
and water. According to the polishing composition in such an embodiment, the polishing
efficiency can be increased by the effect of the basic compound.
[0017] This invention also provides a method for producing a polishing composition comprising
an abrasive, a water-soluble polymer, a basic compound and water. The method comprises
obtaining (which may be preparing, purchasing, receiving) a dispersion comprising
the abrasive, basic composition and water. It also comprises obtaining an aqueous
solution comprising the water-soluble polymer and water. It also comprises adding
and mixing the aqueous solution to the dispersion. Such a production method is a method
for producing the polishing composition comprising grains (which can be the abrasive
alone, abrasive with surrounding water-soluble polymer adhered thereto, abrasive/water-soluble
polymer assemblies) with a volume average particle diameter D
A of 20 nm to 60 nm when measured by dynamic light scattering at a concentration equivalent
to 0.2 % (by mass) abrasive content. The abrasive contains a silica grain and has
an average secondary particle diameter D
P2 of 20 nm to 60 nm, and the polishing composition has a pH of 9.0 to 11.0.
[0018] This invention also provides a method for producing a polished article comprising
supplying a polishing liquid (the term "liquid" herein encompasses a slurry) to a
polishing object and polishing a surface of the polishing object with the polishing
liquid. In the method, as the polishing liquid supplied to the polishing object, a
polishing liquid comprising an abrasive, a water-soluble polymer and water is used.
The polishing liquid comprises, as grains, the abrasive and aggregates formed by adhesion
of the abrasive to the water-soluble polymer. In the polishing liquid, the grains
have a volume average particle diameter D
A of 20 nm to 60 nm when measured by dynamic light scattering. The abrasive contains
a silica grain and has an average secondary particle diameter D
P2 of 20 nm to 60 nm, and the polishing composition has a pH of 9.0 to 11.0. According
to such a production method, because the volume average particle diameter D
A of the grains in the polishing liquid is limited to the prescribed range, the occurrence
of micro defects can be effectively reduced. Accordingly, a polished article can be
provided, having a surface with fewer micro defects.
[0019] The art disclosed herein can be preferably applied to polishing a silicon wafer,
for instance, a lapped silicon wafer. An example of particularly preferable applications
is final polishing of a silicon wafer.
[Description of Embodiments]
[0020] Preferred embodiments of the present invention are described below. Matters necessary
to implement this invention other than those specifically referred to in this specification
may be understood as design matters to a person of ordinary skill in the art based
on the conventional art in the pertinent field. The present invention can be implemented
based on the contents disclosed in this specification and common technical knowledge
in the subject field. In this specification, the terms "weight" and "mass," "% by
weight" and "% by mass," and "parts by weight" and "parts by mass" are used synonymously.
< Abrasive >
[0021] The material and properties of the abrasive in the polishing composition disclosed
herein are not particularly limited and can be suitably selected in accordance with
the purpose and application of the polishing composition. Examples of the abrasive
include inorganic grains, organic grains and organic/inorganic composite grains, provided
that the abrasive contains a silica grain. Specific examples of inorganic grains include
oxide grains such as alumina grains, cerium oxide grains, chromium oxide grains, titanium
dioxide grains, zirconium oxide grains, magnesium oxide grains, manganese dioxide
grains, zinc oxide grains, and red oxide grains; nitride grains such as silicon nitride
grains, and boron nitride grains; carbide grains such as silicon carbide grains, and
boron carbide grains; diamond grains; carbonates such as calcium carbonate, and barium
carbonate. Specific examples of organic grains include polymethyl methacrylate (PMMA)
grains, poly(meth)acrylic acid grains (herein the (meth)acrylic acid comprehensively
means acrylic acid and methacrylic acid), and polyacrylonitrile grains. These abrasives
can be used singly as one species or in a combination of two or more species.
[0022] The abrasive contains a silica grain. Specific examples of silica grains include
colloidal silica, fumed silica, and precipitated silica. From the standpoint of the
less likelihood of scratching the polishing object surface and capability of making
a surface with lower haze, colloidal silica and fumed silica are cited as preferable
silica grains. Colloidal silica is particularly preferable. For instance, colloidal
silica is preferably used as the abrasive in the polishing composition used for polishing
(especially, final polishing) of a silicon wafer.
[0023] The silica constituting the silica grains has a true specific gravity of preferably
1.5 or higher, more preferably 1.6 or higher, or yet more preferably 1.7 or higher.
With increasing true specific gravity of the silica, the polishing rate (amount of
surface removed from article surface per unit time) may increase when polishing a
polishing object (e.g. silicon wafer). From the standpoint of reducing scratches occurring
in the surface (polished surface) of the polishing object, preferable silica grains
have a true specific gravity of 2.2 or lower. As the true specific gravity of the
silica, the value measured by a liquid displacement method using ethanol as the displacing
liquid can be used.
[0024] In the art disclosed herein, the abrasive in the polishing composition can be in
a form of primary particles or in a form of secondary particles which are aggregates
of primary particles. Alternatively, the abrasive may be present both in the primary
particle form and secondary particle form. In a preferable embodiment, the abrasive
is present at least partially in a secondary particle form in the polishing composition.
[0025] In the art disclosed herein, the abrasive's average primary particle diameter D
P1 is not particularly limited as far as it allows the grains in the polishing composition
to satisfy certain conditions of size distribution. In a preferable embodiment, the
abrasive has an average primary particle diameter D
P1 of 5 nm or larger or more preferably 10 nm or larger. With increasing average primary
particle diameter of the abrasive, a higher polishing rate can be obtained. From the
standpoint of obtaining greater effects of polishing (e.g. effects such as reduced
haze, removal of defects), the average primary particle diameter D
P1 is preferably 15 nm or larger, or more preferably 20 nm or larger (e.g. larger than
20 nm). From the standpoint of the likelihood of being present as grains dimensionally
suitable for reduction of micro defects in the polishing composition, the average
primary particle diameter D
P1 is preferably smaller than 35 nm, more preferably 32 nm or smaller, or yet more preferably
30 nm or smaller (e.g. smaller than 30 nm).
[0026] In the art disclosed herein, the average primary particle diameter D
P1 of the abrasive can be determined, for instance, from the specific surface area S
(m
2/g) measured by the BET method by an equation D
P1 = 2720/S (nm). The specific surface area of the abrasive can be measured using, for
instance, a specific surface area analyzer under trade name "FLOW SORB II 2300" available
from Micromeritics.
[0027] The abrasive's average secondary particle diameter D
P2 (which refers to the volume average secondary particle diameter of the abrasive alone)
is as defined in the claims. With increasing average secondary particle diameter D
P2 of the abrasive, a higher polishing rate can be obtained. From the standpoint of
obtaining greater effects of polishing, the average secondary particle diameter D
P2 is preferably 30 nm or larger, more preferably 35 nm or larger, or yet more preferably
40 nm or larger (e.g. larger than 40 nm). From the standpoint of the likelihood of
being present in the polishing composition as grains dimensionally suitable for reduction
of micro defects, the average secondary particle diameter D
P2 is preferably 55 nm or smaller, or more preferably 50 nm or smaller (e.g. smaller
than 50 nm).
[0028] The abrasive's average secondary particle diameter D
P2 can be measured for an aqueous dispersion of the abrasive of interest (but free of
a water-soluble polymer) as a measurement sample by dynamic light scattering using,
for instance, model "UPA-UT151" available from Nikkiso Co., Ltd.
[0029] The abrasive's average secondary particle diameter D
P2 is generally equal to or larger than the abrasive's average primary particle diameter
D
P1 (D
P2/D
P1 ≥ 1) and is typically larger than D
P1 (D
P2/D
P1 > 1). Although not particularly limited, from the standpoint of the effects of polishing
and post-polishing surface smoothness, D
P2/D
P1 of the abrasive is usually suitably in a range of 1.2 to 3, preferably in a range
of 1.5 to 2.5, or more preferably in a range of 1.7 to 2.3 (e.g. greater than 1.9,
but 2.2 or less).
[0030] The abrasive grain's shape (external shape) may be a globular shape or a non-globular
shape. Specific examples of non-globular shapes of the abrasive include a peanut shape
(i.e. peanut shell shape), cocoon shape, confeito shape (spiky ball shape), and rugby
ball shape. For instance, the abrasive mostly comprising peanut-shaped grains can
be preferably used.
[0031] Although not particularly limited, the abrasive has an average value of primary particle's
major axis to minor axis ratio (average aspect ratio) of preferably 1.0 or higher,
more preferably 1.05 or higher, or yet more preferably 1.1 or higher. With increasing
average aspect ratio of the abrasive, a higher polishing rate can be obtained. From
the standpoint of scratch reduction and so on, the abrasive's average aspect ratio
is preferably 3.0 or lower, more preferably 2.0 or lower, or yet more preferably 1.5
or lower.
[0032] The abrasive's shape (external shape) and average aspect ratio can be assessed, for
instance by electron microscope observations. In specific procedures, for instance,
using a scanning electron microscope (SEM), with respect to a prescribed number (e.g.
200) of abrasive grains having observable separate shapes, the smallest circumscribing
rectangles are drawn on the respective grain images. With respect to the rectangle
drawn on each grain image, the long side length (major axis length) is divided by
the short side length (minor axis length) to determine the major axis/minor axis ratio
(aspect ratio). The aspect ratios of the prescribed number of grains can be arithmetically
averaged to determine the average aspect ratio.
< Water-soluble polymer >
[0033] The type of water-soluble polymer in the polishing composition disclosed herein is
not particularly limited. For instance, among water-soluble polymers known in the
field of polishing compositions, one can be selected so as to form grains in desirable
sizes in a polishing composition having an abrasive content of 0.2 % by mass. Water-soluble
polymers can be used singly as one species or in a combination of two or more species.
[0034] The water-soluble polymer may have at least one species of functional group in the
molecule, selected from cation groups, anion groups and nonion groups. In the molecule,
the water-soluble polymer may have, for instance, a hydroxyl group, carboxyl group,
acyloxy group, sulfo group, quaternary nitrogen structure, heterocyclic structure,
vinyl structure, or polyoxyalkylene structure.
[0035] Examples of water-soluble polymers that can be preferably used in the polishing composition
disclosed herein include a cellulose derivative; an oxyalkylene unit-containing polymer;
a polymer comprising an N-vinyl monomeric unit such as N-vinyllactam, open-chain N-vinylamide;
an imine derivative; a polymer comprising a N-(meth)acryloyl monomeric unit; a vinyl
alcohol-based polymer such as polyvinyl alcohol and a derivative thereof; and pullulan.
[0036] Specific examples of the cellulose derivative (or "water-soluble polymer PA" hereinafter)
include hydroxyethyl cellulose, hydroxypropyl cellulose, hydroxyethylmethyl cellulose,
hydroxypropylmethyl cellulose, methyl cellulose, ethyl cellulose, ethylhydroxyethyl
cellulose, and carboxymethyl cellulose. In particular, hydroxyethyl cellulose is preferable.
[0037] The oxyalkylene unit-containing polymer (or "water-soluble polymer PB" hereinafter)
may comprise one, two or more species of oxyalkylene unit with 2 to 6 carbon atoms
(typically, a structural unit represented by -C
nH
2nO- wherein n is an integer between 2 and 6). The number of carbon atoms in the oxyalkylene
unit is preferably 2 to 3. Examples of such a polymer include a polyethylene oxide,
a block copolymer of ethylene oxide (EO) and propylene oxide (PO), and a random copolymer
of EO and PO.
[0038] The block copolymer of EO and PO can be a diblock copolymer, triblock copolymer or
the like comprising a polyethylene oxide block (PEO) and a polypropylene oxide block
(PPO). Examples of the triblock copolymer include a PEO-PPO-PEO triblock copolymer
and PPO-PEO-PPO triblock copolymer. Usually, a PEO-PPO-PEO triblock copolymer is more
preferable.
[0039] As the PEO-PPO-PEO triblock copolymer, a polymer represented by the following formula
(1) can be preferably used:
HO-(EO)
a-(PO)
b(EO)
c-H (1)
[0040] In the general formula (1), EO represents an oxyethylene unit (-CH
2CH
2O-), PO represents an oxypropylene unit (-CH
2CH(CH
3)O-), and each of a, b and c is an integer of 1 or higher (typically 2 or higher).
[0041] In the general formula (1), the total of a and c is preferably in a range of 2 to
1000, more preferably in a range of 5 to 500, or yet more preferably in a range of
10 to 200. In the general formula (1), b is preferably in a range of 2 to 200, more
preferably in a range of 5 to 100, or yet more preferably in a range of 10 to 50.
[0042] In the block copolymer or random copolymer of EO and PO, from the standpoint of the
water solubility and washability, the molar ratio (EO/PO) between EO and PO constituting
the copolymer is preferably higher than 1, more preferably 2 or higher, or yet more
preferably 3 or higher (e.g. 5 or higher).
[0043] Examples of the N-vinyl monomeric unit-containing polymer (or "water-soluble polymer
PC" hereinafter) include a homopolymer of an N-vinyllactam-based monomer and a copolymer
thereof (e.g. a copolymer in which the copolymerization ratio of the N-vinyllactam-based
monomer exceeds 50 % by weight), and a homopolymer of an open-chain N-vinylamide and
a copolymer thereof (e.g. a copolymer in which the copolymerization ratio of the open-chain
N-vinylamide exceeds 50 % by weight).
[0044] Unless otherwise indicated, the copolymer in this specification comprehensively means
various copolymers such as random copolymer, alternating copolymer, block copolymer,
and graft copolymer.
[0045] Specific examples of the N-vinyllactam-based monomer include N-vinylpyrrolidone (VP),
N-vinylpiperidone, N-vinylmorpholinone, N-vinylcaprolactam (VC), N-vinyl-1,3-oxazine-2-one,
and N-vinyl-3,5-morpholinedione. Specific examples of the N-vinyllactam monomeric
unit-containing polymer include a polyvinylpyrrolidone, polyvinylcaprolactam, random
copolymer of VP and VC, random copolymer of one or each of VP and VC with another
vinyl monomer (e.g. acrylic monomer, vinyl ester-based monomer), and block copolymer
and graft copolymer comprising a polymer segment with one or each of VP and VC (e.g.
a graft copolymer obtained by grafting polyvinyl alcohol with polyvinylpyrrolidone).
A particularly preferable species is a vinylpyrrolidone-based polymer (PVP). Herein
the vinylpyrrolidone-based polymer refers to a VP homopolymer and a VP copolymer (e.g.
a copolymer in which the copolymerization ratio of VP exceeds 50 % by weight). In
the vinylpyrrolidone-based polymer, the molar ratio of VP units to all the repeating
units is usually 50 % or higher and suitably 80 % or higher (e.g. 90 % or higher,
typically 95 % or higher). Essentially all the repeating units in the water-soluble
polymer may be formed with VP units.
[0046] Specific examples of the open-chain N-vinylamide include N-vinylacetamide, N-vinylpropionic
acid amide, and N-vinyllactic acid amide.
[0047] The imine derivative (or "water-soluble polymer PD" hereinafter) includes a homopolymer
and a copolymer of an N-acylalkyleneimine-based monomer. Specific examples of the
N-acylalkyleneimine-based monomer include N-acetylethyleneimine, N-propionylethyleneimine,
N-caproylethyleneimine, N-benzoylethyleneimine, N-acetylpropyleneimine, and N-butyrylethyleneimine.
As the homopolymer of N-acylalkyleneimine-based monomer, a poly(N-acylalkyleneimine)
and the like can be used. Specific examples include poly(N-acetylethyleneimine), poly(N-propionylethyleneimine),
poly(N-caproylethyleneimine), poly(N-benzoylethyleneimine), poly(N-acetylpropyleneimine),
and poly(N-butyrylethyleneimine). Examples of the copolymer of N-acylalkyleneimine-based
monomer include a copolymer of two or more species of N-acylalkyleneimine-based monomer
and a copolymer of one, two or more species of N-acylalkyleneimine-based monomer and
other monomer(s).
[0048] Examples of the N-(meth)acryloyl monomeric unit-containing polymer (or "water-soluble
polymer PE" hereinafter) include a homopolymer of an N-(meth)acryloyl-based monomer
and a copolymer thereof (typically a copolymer in which the copolymerization ratio
of N-(meth)acryloyl-based monomer exceeds 50 % by weight). Examples of the N-(meth)acryloyl-based
monomer include an open-chain amide having an N-(meth)acryloyl group and a cyclic
amide having an N-(meth)acryloyl group.
[0049] Examples of an open-chain amide having an N-(meth)acryloyl group include: acrylamide;
N-monoalkylacrylamides such as N-methylacrylamide, N-ethylacrylamide, N-propylacrylamide,
N-isopropylacrylamide, N-butylacrylamide, N-isobutylacrylamide, N-tert-butylacrylamide,
N-heptylacrylamide, N-octylacrylamide, N-tert-octylacrylamide, N-dodecylacrylamide,
and N-octadecylacrylamide; substituted N-monoalkylacrylamides such as N-(2-hydroxyethyl)acrylamide,
N-(1,1-dimethyl-2-hydroxyethyl)acrylamide, N-(1-ethyl-hydroxyethyl)acrylamide, N-(2-chloroethyl)acrylamide,
N-(2,2,2-trichloro-1-hydroxyethyl)acrylamide, N-(2-dimethylaminoethyl)acrylamide,
N-(3-dimethylaminopropyl)acrylamide, N-[3-bis(2-hydroxyethyl)aminopropyl]acrylamide,
N-(1,1-dimethyl-2-dimethylaminoethyl)acrylamide, N-(2-methyl-2-phenyl-3-dimethylaminopropyl)acrylamide,
N-(2,2-dimethyl-3-dimethylaminopropyl)acrylamide, N-(2-morpholinoethyl)acrylamide,
and N-(2-amino-1,2-dicyanoethyl)acrylamide; N-monoalkenylacrylamides such as N-allylacrylamide;
N-monoalkynylacrylamides such as N-(1,1-dimethylpropynyl)acrylamide; aromatic group-containing
acrylamides such as N-phenylacrylamide, N-benzylacrylamide, and N-[4-(phenylamino)phenyl]acrylamide;
N-monoalkylolacrylamides such as N-methylolacrylamide, N-ethylolacrylamide, N-propylolacrylamide,
etc.; N-alkoxyalkylacrylamides such as N-methoxymethylacrylamide, N-ethoxymethylacrylamide,
N-butoxymethylacrylamide, and N-isobutoxymethylacrylamide; N-alkoxyacrylamides such
as N-methoxyacrylamide, N-ethoxyacrylamide, N-propoxyacrylamide, and N-butoxyacrylamide;
N-acetylacrylamide; N-diacetoneacrylamide; methacrylamide; N-monoalkylmethacrylamides
such as N-methylmethacrylamide, N-ethylmethacrylamide, N-propylmethacrylamide, N-isopropylmethacrylamide,
N-butylmethacrylamide, N-isobutylmethacrylamide, N-tert-butylmethacrylamide, N-heptylmethacrylamide,
N-octylmethacrylamide, N-tert-octylmethacrylamide, and N-dodecylmethacrylamide, N-octadecylmethacrylamide;
substituted N-monoalkylmethacrylamides such as N-(2-hydroxyethyl)methacrylamide, N-(1,1-dimethyt-2-hydroxyethyt)methacrytamide,
N-(1-ethylhydroxyethyl)methacrylamide, N-(2-chloroethyl)methacrylamide, N-(2,2,2-trichloro-1-hydroxyethyl)methacrylamide,
N-(2-dimethylaminoethyl)methacrylamide, N-(3-dimethylaminopropyl)methacrylamide, N-[3-bis(2-hydroxyethyl)aminopropyl]methacrylamide,
N-(1,1-dimethyl-2-dimethylaminoethyl)methacrylamide, N-(2-methyl-2-phenyl-3-dimethylaminopropyl)methacrylamide,
N-(2,2-dimethyl-3-dimethylaminopropyl)methacrylamide, N-(2-morpholinoethyl)methacrylamide,
and N-(2-amino-1,2-dicyanoethyl)methacrylamide; N-monoalkenylmethacrylamides such
as N-allylmethacrylamide; N-monoalkynylmethacrylamides such as N-(1,1-dimethylpropynyl)methacrylamide;
aromatic group-containing methacrylamides such as N-phenylmethacrylamide, N-benzylmethacrylamide,
and N-[4-(phenylamino)phenyl]methacrylamide; N-monoalkylolmethacrylamides such as
N-methylolmethacrylamide, N-ethylolmethacrylamide, and N-propylolmethacrylamide; N-alkoxyalkylmethacrylamides
such as N-methoxymethylmethacrylamide, N-ethoxymethylmethacrylamide, N-butoxymethylmethacrylamide,
N-isobutoxymethylmethacrylamide, etc.; N-alkoxymethacrylamides such as N-methoxymethacrylamide,
N-ethoxymethacrylamide, N-propoxymethacrylamide, and N-butoxymethacrylamide; N-acetylmethacrylamide;
N-diacetonemethacrylamide; N,N-dialkylacrylamides such as N,N-dimethylacrylamide,
N,N-diethylacrylamide, N,N-dipropytacrylamide, N,N-diisopropylacrylamide, N,N-dibutylacrylamide,
N,N-diisobutylacrylamide, N,N-di-tert-butylacrylamide, N,N-diheptylacrylamide, N,N-dioctylacrylamide,
N,N-di-tert-octylacrylamide, N,N-didodecylacrylamide, and N,N-dioctadecylacrylamide;
N,N-dialkylaminoalkylacrylamides such as N,N-dimethylaminoethylacrylamide, N,N-diethylaminoethylacrylamide,
N,N-dimethylaminopropylacrylamide, and N,N-diethylaminopropylacrylamide; substituted
N,N-dialkylacrylamides such as N,N-bis(2-hydroxyethyl)acrylamide, and N,N-bis(2-cyanoethyl)acrylamide;
N,N-dialkenylacrylamides such as N,N-diallylacrylamide; aromatic group-containing
acrylamides such as N,N-diphenylacrylamide, and N,N-dibenzylacrylamide; N,N-dialkylolacrylamides
such as N,N-dimethylolacrylamide, N,N-diethylolacrylamide, and N,N-dipropylolacrylamide;
N-alkoxy-N-alkylacrylamides such as N-methyl-N-methoxyacrylamide, N-methyl-N-ethoxyacrylamide,
N-methyl-N-propoxyacrylamide, N-methyl-N-butoxyacrylamide, N-ethyl-N-methoxyacrylamide,
N-ethyl-N-ethoxyacrylamide, N-ethyl-N-butoxyacrylamide, N-propyl-N-methoxyacrylamide,
N-propyl-N-ethoxyacrylamide, N-butyl-N-methoxyacrylamide, and N-butyl-N-ethoxyacrylamide;
N,N-diacetylacrylamide; N,N-diacetoneacrylamide; N,N-dialkylmethacrylamides such as
N,N-dimethylmethacrylamide, N,N-diethylmethacrylamide, N,N-dipropylmethacrylamide,
N,N-diisopropylmethacrylamide, N,N-dibutylmethacrylamide, N,N-diisobutylmethacrylamide,
N,N-di-tert-butylmethacrylamide, N,N-diheptylmethacrylamide, N,N-dioctylmethacrylamide,
N,N-di-tert-octylmethacrylamide, N,N-didodecylmethacrylamide, and N,N-dioctadecylmethacrylamide;
N,N-dialkylaminoalkylmethacrylamides such as N,N-dimethylaminoethylmethacrylamide,
N,N-diethylaminoethylmethacrylamide, N,N-dimethylaminopropylmethacrylamide, and N,N-diethylaminopropylmethacrylamide;
substituted N,N-dialkylmethacrylamides such as N,N-bis(2-hydroxyethyl)methacrylamide,
and N,N-bis(2-cyanoethyl)methacrylamide; N-dialkenylmethacrylamides such as N,N-diallylmethacrylamide;
aromatic group-contaning methacrylamides such as N,N-diphenylmethacrylamide, and N,N-dibenzylmethacrylamide;
N,N-dialkylolmethacrylamides such as N,N-dimethylolmethacrylamide, N,N-diethylolmethacrylamide,
and N,N-dipropylolmethacrylamide; N-alkoxy-N-alkylmethacrylamides such as N-methyl-N-methoxymethacrylamide,
N-methyl-N-ethoxymethacrylamide, N-methyl-N-propoxymethacrylamide, N-methyl-N-butoxymethacrylamide,
N-ethyl-N-methoxymethacrylamide, N-ethyl-N-ethoxymethacrylamide, N-ethyl-N-butoxymethacrylamide,
N-propyl-N-methoxymethacrylamide, N-propyl-N-ethoxymethacrylamide, N-butyl-N-methoxymethacrylamide,
and N-butyl-N-ethoxymethacrylamide; N,N-diacetylmethacrylamide; and N,N-diacetonemethacrylamide.
[0050] Examples of a polymer comprising a N-(meth)acryloyl group-containing open-chain amide
as a monomeric unit include a homopolymer of N-isopropylacrylamide and a copolymer
of N-isopropylacrylamide (e.g. a copolymer in which the copolymerization ratio of
N-isopropylacrylamide exceeds 50 % by weight).
[0051] Examples of the N-(meth)acryloyl group-containing cyclic amide include N-acryloylmorpholine,
N-acryloylthiomorpholine, N-acryloylpiperidine, N-acryloylpyrrolidine, N-methacryloylmorpholine,
N-methacryloylpiperidine, and N-methacryloylpyrrolidine. An example comprising an
N-(meth)acryloyl group-containing cyclic amide as a monomeric unit is an acryloylmorpholine-based
polymer (PACMO). Typical examples of the acryloylmorpholine-based polymer include
a homopolymer of N-acryloylmorpholine (ACMO) and a copolymer of ACMO (e.g. a copolymer
in which the copolymerization ratio of ACMO exceeds 50 % by weight). In the acryloylmorpholine-based
polymer, the molar ratio of ACMO units to all the repeating units is usually 50 %
or higher and suitably 80 % or higher (e.g. 90 % or higher, typically 95 % or higher).
Essentially all the repeating units in the water-soluble polymer may be formed with
ACMO units.
[0052] The vinyl alcohol-based polymer (or "water-soluble polymer PF' hereinafter) (PVA)
typically comprises a vinyl alcohol unit (VA unit) as the primary repeating unit.
In this polymer, the molar ratio of VA units to all the repeating units is usually
50 % or higher, preferably 65 % or higher, or more preferably 70 % or higher, for
instance, 75 % or higher. Essentially all the repeating units may be formed with VA
units. In the water-soluble polymer PF, the type(s) of repeating unit(s) other than
the VA unit are not particularly limited. Examples include vinyl acetate unit, vinyl
propionate unit, vinyl hexanoate unit.
[0053] PVA has a degree of saponification of usually 50 % by mole or higher, preferably
65 % by mole or higher, or more preferably 70 % by mole or higher, for instance, 75
% by mole or higher. The degree of saponification of PVA is theoretically 100 % by
mole or lower.
[0054] The polishing composition disclosed herein can be preferably made in an embodiment
comprising, as the water-soluble polymer, for instance, at least a water-soluble polymer
PA and/or a water-soluble polymer PF. A preferable embodiment comprises at least a
water-soluble polymer PA (typically hydroxyethyl cellulose) as the water-soluble polymer.
For example, an embodiment that comprises a water-soluble polymer PA solely, an embodiment
comprising a water-soluble polymer PA and a water-soluble polymer PC, an embodiment
comprising a water-soluble polymer PA and a water-soluble polymer PE, and like embodiment
can be employed. In a preferable example of such a polishing composition, the primary
component (typically the component accounting for more than 50 % by mass) of the water-soluble
polymer is hydroxyethyl cellulose. Of the water-soluble polymer, hydroxyethyl cellulose
may account for 60 % by mass or higher, for instance, 80 % by mass or higher, or more
preferably 90 % by mass or higher. 100 % by mass of the water-soluble polymer may
be hydroxyethyl cellulose. Another preferable embodiment comprises at least a water-soluble
polymer PF as the water-soluble polymer. For example, an embodiment that comprises
a water-soluble polymer PF solely, an embodiment comprising a water-soluble polymer
PF and a water-soluble polymer PC, an embodiment comprising a water-soluble polymer
PF and a water-soluble polymer PA, and like embodiment can be employed. Another preferable
embodiment of the polishing composition disclosed herein comprises a water-soluble
polymer PE solely as the water-soluble polymer.
[0055] In the polishing composition disclosed herein, the molecular weight of the water-soluble
polymer is not particularly limited. For instance, a water-soluble polymer having
a weight average molecular weight (Mw) of 200 × 10
4 or smaller (typically 1 × 10
1 to 200 × 10
4, e.g. 1 × 10
3 to 150 × 10
4) can be used. From the standpoint of the likelihood of forming grains in suitable
sizes disclosed herein, the use of a water-soluble polymer having a Mw of smaller
than 100 × 10
4 (more preferably 80 × 10
4 or smaller, yet more preferably 50 × 10
4 or smaller, typically 40 × 10
4 or smaller) is preferable. From the standpoint of the ease of filtering and washing
the polishing composition, a water-soluble polymer having a Mw of 30 × 10
4 or smaller (typically smaller than 30 × 10
4) can be preferably used. On the other hand, in general, with increasing Mw of water-soluble
polymer, the haze reduction effect tends to increase. From such a standpoint, it is
usually suitable to use a water-soluble polymer having a Mw of 1 × 10
1 or larger. For instance, a water-soluble polymer having a Mw of 1 × 10
4 or larger can be preferably used.
[0056] More preferable Mw ranges may also vary depending on the type of water-soluble polymer.
For instance, the Mw of water-soluble polymer PA is typically smaller than 100 × 10
4, preferably 80 × 10
4 or smaller, more preferably 50 × 10
4 or smaller, or yet more preferably 30 × 10
4 or smaller (typically smaller than 30 × 10
4). The Mw of water-soluble polymer PA is typically 1 × 10
4 or larger, preferably 2 × 10
4 or larger, more preferably 3 × 10
4 or larger, or yet more preferably 5 × 10
4 or larger (e.g. 7 × 10
4 0r larger). For instance, the Mw of water-soluble polymer PB is preferably 50 × 10
4 or smaller, more preferably 30 × 10
4 or smaller, or yet more preferably 20 × 10
4 or smaller. The Mw of water-soluble polymer PB is typically 1 × 10
4 or larger. For instance, the Mw of water-soluble polymer PC is typically 15 × 10
4 or smaller, preferably 10 × 10
4 or smaller, or more preferably 8 × 10
4 or smaller. A water-soluble polymer PC having a Mw of 5 × 10
4 or smaller (e.g. 3 × 10
4 or smaller) can be used as well. The Mw of water-soluble polymer PC is typically
1 × 10
4 or larger. For instance, the Mw of water-soluble polymer PD is preferably 30 × 10
4 or smaller, more preferably 20 × 10
4 or smaller, or yet more preferably 10× 10
4 or smaller (e.g. 5 × 10
4 or smaller). The Mw of water-soluble polymer PD is typically 1 × 10
4 or larger. For instance, the Mw of water-soluble polymer PE is typically 40 × 10
4 or smaller, preferably 20 × 10
4 or smaller, or more preferably 10 × 10
4 or smaller. The Mw of water-soluble polymer PE is typically 1 × 10
4 or larger. For instance, the Mw of water-soluble polymer PF (PVA) is typically 6
× 10
4 or smaller, preferably 5.5 × 10
4 or smaller, or more preferably 3 × 10
4 or smaller (e.g. 2 × 10
4 or smaller). The Mw of water-soluble polymer PF is typically 1 × 10
3 or larger, or preferably 3 × 10
3 or larger, for example, 4 × 10
1 or larger. A water-soluble polymer PF having a Mw of 1 × 10
4 or larger can be used as well.
[0057] In the art disclosed herein, the relationship between the weight average molecular
weight (Mw) and number average molecular weight (Mn) of the water-soluble polymer
is not particularly limited. For instance, a polymer having Mw and Mn satisfying the
next equation Mw/Mn ≤ 5.0 can be preferably used. From the standpoint of the performance
stability of the polishing composition, the Mw/Mn of the water-soluble polymer is
preferably 4.8 or smaller, or more preferably 4.6 or smaller. Theoretically, the Mw/Mn
is 1.0 or greater. As the Mw and Mn of the water-soluble polymer, the values based
on GPC (aqueous, based on standard polyethylene oxide) can be used.
[0058] More preferable ranges of the Mw/Mn may also vary depending on the type of water-soluble
polymer. For instance, the Mw/Mn of water-soluble polymer PA is preferably 4.8 or
lower, or more preferably 4.6 or lower. For instance, the Mw/Mn of water-soluble polymer
PB is preferably 4.0 or lower, more preferably 3.5 or lower, or yet more preferably
3.0 or lower. For instance, the Mw/Mn of water-soluble polymer PC is preferably 4.0
or lower, more preferably 3.5 or lower, or yet more preferably 3.0 or lower. For instance,
the Mw/Mn of water-soluble polymer PD is preferably 4.0 or lower, more preferably
3.5 or lower, or yet more preferably 3.0 or lower. For instance, the Mw/Mn of water-soluble
polymer PE is preferably 4.0 or lower, more preferably 3.5 or lower, or yet more preferably
3.0 or lower.
[0059] On the other hand, for instance, the Mw/Mn of water-soluble polymer PA is preferably
2.0 or higher, or more preferably 3.0 or higher. For instance, the Mw/Mn of water-soluble
polymer PB is preferably 1.05 or higher. For instance, the Mw/Mn of water-soluble
polymer PC is preferably 1.05 or higher. For instance, the Mw/Mn of water-soluble
polymer PD is preferably 1.05 or higher. For instance, the Mw/Mn of water-soluble
polymer PE is preferably 1.05 or higher.
[0060] The Mw/Mn of water-soluble polymer PF is preferably 4.0 or lower, more preferably
3.5 or lower, or yet more preferably 3.0 or lower. The Mw/Mn of water-soluble polymer
PF is preferably 1.05 or higher.
[0061] As the Mw and Mn of a water-soluble polymer, the values based on aqueous gel permeation
chromatography (GPC) (aqueous, based on standard polyethylene oxide) can be used.
[0062] Although not particularly limited, the water-soluble polymer content can be, for
instance, 0.01 part by mass or higher to 100 parts by mass of the abrasive. From the
standpoint of increasing the post-polishing surface smoothness (e.g. reduction of
haze and defects), the water-soluble polymer content relative to 100 parts by mass
of the abrasive is suitably 0.05 part by mass or higher, preferably 0.1 part by mass
or higher, or more preferably 0.5 part by mass or higher (e.g. 1 part by mass or higher).
From the standpoint of the polishing rate and washability, the water-soluble polymer
content relative to 100 parts by mass of the abrasive can be, for instance, 40 parts
by mass or less, usually suitably 20 parts by mass or less, preferably 15 parts by
mass or less, or more preferably 10 parts by mass or less.
< Water >
[0063] As the water in the polishing composition disclosed herein, ion-exchanged water (deionized
water), pure water, ultrapure water, and distilled water can be preferably used. To
avoid hindering the effects of other components in the polishing composition whenever
possible, in the water used, for instance, the total transition metal ion content
is preferably 100 ppb or less. For example, the purity of the water can be increased
by operations such as removing impurity ions with ion-exchange resin, removing contaminants
with a filter, distillation, and so on.
[0064] The polishing composition disclosed herein may further comprise, as necessary, a
water-miscible organic solvent (lower alcohol, lower ketone). In usual, of the solvent
in the polishing composition, preferably 90 % by volume or more is water, or more
preferably 95 % by volume or more (typically 99 to 100 % by volume) is water.
[0065] The polishing composition disclosed herein (typically a slurry composition) can be
preferably made, for instance, in an embodiment in which the non-volatile content
(NV) is 0.01 % by mass to 50 % by mass and the rest is an aqueous solvent (water or
a mixture of water and the organic solvent) or in an embodiment where the rest is
an aqueous solvent and a volatile compound (e.g. ammonia). An embodiment wherein the
NV is 0.05 % by mass to 40 % by mass is more preferable. The non-volatile content
(NV) refers to the mass proportion of residue remaining in the polishing composition
after drying the polishing composition at 105 °C for 24 hours.
< Basic compound >
[0066] The polishing compound disclosed herein typically comprises a basic compound besides
the abrasive, water-soluble polymer and water. Herein, the basic compound refers to
a compound having an ability to increase the pH of a polishing composition upon addition
to the composition. The basic compound may work to chemically polish the target surface
and contribute to increase the polishing rate. The basic compound may also help increase
the dispersion stability of the polishing composition.
[0067] As the basic compound, organic or inorganic nitrogen-containing basic compounds,
hydroxides of alkali metals or alkaline earth metals, various carbonates and hydrogen
carbonates, can be used. Examples include alkali metal hydroxides; quaternary ammonium
hydroxides and salts thereof; ammonia; and amines. Specific examples of alkali metal
hydroxides include potassium hydroxide, and sodium hydroxide. Specific examples of
carbonates and hydrogen carbonates include ammonium hydrogen carbonate, ammonium carbonate,
potassium hydrogen carbonate, potassium carbonate, sodium hydrogen carbonate, and
sodium carbonate. Specific examples of quaternary ammonium hydroxides or salts thereof
include such as tetramethylammonium hydroxide, tetraethylammonium hydroxide, and tetrabutylammonium
hydroxide. Specific examples of amines include methylamine, dimethylamine, trimethylamine,
ethylamine, diethylamine, triethylamine, ethylenediamine, monoethanolamine, N-(β-aminoethyl)ethanolamine,
hexamethylenediamine, diethylenetriamine, triethylenetetraamine, anhydrous piperazine,
piperazine hexahydrate, 1-(2-aminoethyl)piperazine, N-methylpiperazine, guanidine,
azoles such as imidazole, and triazole. These basic compounds can be used singly as
one species or in a combination of two or more species.
[0068] Examples of basic compounds preferable from the standpoint of increasing the polishing
rate, include ammonia, potassium hydroxide, sodium hydroxide, tetramethylammonium
hydroxide, tetraethylammonium hydroxide, ammonium hydrogen carbonate, ammonium carbonate,
potassium hydrogen carbonate, potassium carbonate, sodium hydrogen carbonate and sodium
carbonate. In particular, preferable examples include ammonia, potassium hydroxide,
sodium hydroxide, tetramethylammonium hydroxide and tetraethylammonium hydroxide.
As more preferable species, ammonia and tetramethylammonium hydroxide are cited. An
especially preferable basic compound is ammonia.
< Surfactant >
[0069] The polishing composition disclosed herein can be preferably made in an embodiment
comprising a surfactant (typically a water-soluble organic compound having a molecular
weight below 1 × 10
4) besides the abrasive, water-soluble polymer and water. The use of surfactant may
increase the dispersion stability of the polishing composition. It may facilitate
the reduction of haze. For the surfactant, solely one species or a combination of
two or more species can be used.
[0070] As the surfactant, anionic or nonionic kinds can be preferably used. From the standpoint
of the low-foaming properties and easy pH adjustment, nonionic surfactants are more
preferable. Examples include oxyalkylene polymers such as polyethylene glycol, polypropylene
glycol, and polytetramethylene glycol; polyoxyalkylene adducts such as polyoxyethylene
alkyl ether, polyoxyethylene alkyl phenyl ether, polyoxyethylene alkylamine, polyoxyethylene
fatty acid ester, polyoxyethylene glyceryl ether fatty acid ester, and polyoxyethylene
sorbitan fatty acid ester; and copolymers (diblock copolymer, triblock copolymer,
random copolymer, alternating copolymer) of several species of oxyalkylene.
[0071] Specific examples of nonionic surfactant include a block copolymer of EO and PO (diblock
copolymer, PEO-PPO-PEO triblock copolymer, or PPO-PEO-PPO triblock copolymer), a random
copolymer of EO and PO, polyoxyethylene glycol, polyoxyethylene propyl ether, polyoxyethylene
butyl ether, polyoxyethylene pentyl ether, polyoxyethylene hexyl ether, polyoxyethylene
octyl ether, polyoxyethylene 2-ethylhexyl ether, polyoxyethylene nonyl ether, polyoxyethylene
decyl ether, polyoxyethylene isodecyl ether, polyoxyethylene tridecyl ether, polyoxyethylene
lauryl ether, polyoxyethylene cetyl ether, polyoxyethylene stearyl ether, polyoxyethylene
isostearyl ether, polyoxyethylene oleyl ether, polyoxyethylene phenyl ether, polyoxyethylene
octyl phenyl ether, polyoxyethylene nonyl phenyl ether, polyoxyethylene dodecyl phenyl
ether, polyoxyethylene styrenated phenyl ether, polyoxyethylene laurylamine, polyoxyethylene
stearylamine, polyoxyethylene oleylamine, polyoxyethylene stearylamide, polyoxyethylene
oleylamide, polyoxyethylene monolaurate, polyoxyethylene monostearate, polyoxyethylene
distearate, polyoxyethylene monooleate, polyoxyethylene dioleate, polyoxyethylene
sorbitan monolaurate, polyoxyethylene sorbitan monopalmitate, polyoxyethylene sorbitan
monostearate, polyoxyethylene sorbitan monooleate, polyoxyethylenesorbitan trioleate,
polyoxyethylene sorbitol tetraoleate, polyoxyethylene castor oil, and polyoxyethylene
hardened castor oil. Particularly preferable surfactants include a block copolymer
of EO and PO (especially a PEO-PPO-PEO triblock copolymer), a random copolymer of
EO and PO, and polyoxyethylene alkyl ether (e.g. polyoxyethylene decyl ether).
[0072] The surfactant typically has a molecular weight below 1 × 10
4. From the standpoint of the ease of filtering the polishing composition and washing
the polished article, it is preferably 9500 or smaller. The molecular weight of the
surfactant is typically 200 or larger. From the standpoint of haze reduction effect,
it is preferably 250 or larger, or more preferably 300 or larger (e.g. 500 or larger).
As the molecular weight of the surfactant, the weight average molecular weight (Mw)
determined by GPC (aqueous, based on standard polyethylene glycol) or the molecular
weight determined from the chemical formula can be used.
[0073] More preferable molecular weight ranges of the surfactant may also vary depending
on the type of surfactant. For instance, when a block copolymer of EO and PO is used
as the surfactant, its Mw is preferably 1000 or larger, more preferably 2000 or larger,
or yet more preferably 5000 or larger.
[0074] When the polishing composition disclosed herein comprises a surfactant, its content
is not particularly limited as far as the effects of the present invention are not
significantly impaired. Usually, from the standpoint of the washability, the surfactant
content relative to 100 parts by mass of the abrasive is suitably 20 parts by mass
or less, preferably 15 parts by mass or less, or more preferably 10 parts by mass
or less (e.g. 6 parts by mass or less). From the standpoint of obtaining greater effects
of using the surfactant, the surfactant content relative to 100 parts by mass of the
abrasive is suitably 0.001 part by mass or greater, preferably 0.005 part by mass
or greater, or more preferably 0.01 part by mass or greater (e.g. 0.05 part by mass
or greater, typically 0.1 part by mass or greater).
[0075] The mass ratio (W1/W2) of water-soluble polymer content W1 to surfactant content
W2 is not particularly limited. Usually, it is suitably in a range of 0.01 to 200,
or preferably, for instance, in a range of 0.1 to 100. In a preferable embodiment,
W1/W2 can be, for instance, in a range of 0.01 to 20, preferably in a range of 0.05
to 15, or more preferably in a range of 0.1 to 10.
< Other components >
[0076] As far as the effects by the present invention are not significantly hindered, the
polishing composition disclosed herein may further comprise as necessary known additives,
such as chelating agents, organic acids, organic acid salts, inorganic acids, inorganic
acid salts, preservatives, antifungal agents, and so on, which can be used in polishing
compositions (typically, polishing compositions used for final polishing of silicon
wafers).
[0077] Examples of chelating agents include aminocarboxylic acid-based chelating agents
and organophosphonic acid-based chelating agents. Examples of aminocarboxylic acid-based
chelating agents include ethylenediamine tetraacetic acid, ethylenediamine tetraacetic
acid sodium salt, nitrilotriacetic acid, nitrilotriacetic acid sodium salt, nitrilotriacetic
acid ammonium salt, hydroxyethylethylenedimaine triacetic acid, hydroxyethylethylenediamine
triacetic acid sodium salt, diethylenetriamine pentaacetic acid, diethylenetriamine
pentaacetic acid sodium salt, triethylenetetramine hexaacetic acid, and triethylenetetramine
hexaacetic acid sodium salt. Examples of organophosphonic acid-based chelating agents
include 2-aminoethylphosphonic acid, 1-hydroxyethylidene-1,1-diphosphonic acid, aminotri(methylenephosphonic
acid), ethylenediaminetetrakis(methylenephosphonic acid), diethylenetriaminepenta(methylenephosphonic
acid), ethane-1,1-diphosphonic acid, ethane-1,1,2-triphosphonic acid, ethane-1-hydroxy-1,1-diphosphonic
acid, ethane-1-hydroxy-1,1,2-triphosphonic acid, ethane-1,2-dicarboxy-1,2-diphosphonic
acid, methanehydroxyphosphonic acid, 2-phosphonobutane-1,2-dicarboxylic acid, 1-phosphonobutane-2,3,4-tricarboxylic
acid, and α-methylphosphonosuccinic acid. Among them, organophosphonic acid-based
chelating agents are preferable, with ethylenediaminetetrakis(methylenephosphonic
acid) and diethylenetriaminepenta(methylenephosphonic acid) being more preferable.
A particularly preferable chelating agent is ethylenediaminetetrakis(methylenephosphonic
acid).
[0078] Examples of organic acids include aliphatic acids such as formic acid, acetic acid,
propionic acid; aromatic carboxylic acids such as benzoic acid, and phthalic acid;
as well as citric acid, oxalic acid, tartaric acid, malic acid, maleic acid, fumaric
acid, succinic acid, organic sulfonic acids, and organic phosphoric acids. Examples
of organic acid salts include alkali metal salts (sodium salts, or potassium salts),
and ammonium salts of organic acids. Examples of inorganic acids include sulfuric
acid, nitric acid, hydrochloric acid, carbonic acid. Examples of inorganic acid salts
include alkali metal salts (sodium salts, potassium salts) and ammonium salts of inorganic
acids. The organic acids and their salts as well as inorganic acids and their salts
can be used singly as one species or in a combination of two or more species.
[0079] Examples of preservatives and antifungal agents include isothiazoline-based compounds,
paraoxybenzoic acid esters, and phynoxyethanol.
< Applications >
[0080] The polishing composition disclosed herein can be suitably applied for polishing
objects of various materials and shapes. The polishing object's material can be, for
instance, a metal or metalloid such as silicon, aluminum, nickel, tungsten, copper,
tantalum, titanium, stainless steel, or an alloy of these; a glassy material such
as quartz glass, aluminosilicate glass, glassy carbon; a ceramic material such as
alumina, silica, sapphire, silicon nitride, tantalum nitride, titanium carbide; material
for compound semiconductor substrates such as silicon carbide, gallium nitride, gallium
arsenide; a resin material such as polyimide resin. The polishing object may be formed
of several materials among them. In particular, it is suitable for polishing a polishing
object having a surface formed of silicon.
[0081] The shape of the polishing object is not particularly limited. The polishing composition
disclosed herein can be preferably applied for polishing a polishing object having
a flat surface such as a plate, or polyhedron.
[0082] The polishing composition disclosed herein can be preferably used for final polishing
of a polishing object. Accordingly, this specification provides a polished article
production method (e.g. silicon wafer production method) comprising a final polishing
step using the polishing composition. The final polishing refers to the last polishing
step (i.e. a step after which no further polishing is performed) in a production process
of a polishing object of interest. The polishing composition disclosed herein may
be used in an earlier polishing step than final polishing (referring to a step between
the rough polishing step and final polishing step, typically including at least a
first polishing step and possibly second, third ...polishing steps), for instance,
in a polishing step performed just before final polishing.
[0083] The polishing composition disclosed herein can be particularly preferably used for
polishing a silicon wafer. For instance, it is preferable as a polishing composition
used in final polishing of a silicon wafer or in an earlier polishing step than this.
For instance, it is effectively applied for polishing (typically final polishing or
polishing just before this) of a silicon wafer prepared into a surface state having
a surface roughness of 0.01 nm to 100 nm in an earlier step. It is particularly preferably
applied to final polishing.
< Polishing liquid >
[0084] The polishing composition disclosed herein is supplied to a polishing object, typically
in a form of a polishing liquid comprising the polishing composition, and used for
polishing the polishing object. The polishing liquid may be prepared, for instance,
by diluting (typically with water) a polishing composition disclosed herein. Alternatively,
the polishing composition can be used straight as a polishing liquid. In other words,
the concept of polishing composition in the art disclosed herein encompasses both
a polishing liquid (working slurry) supplied to a polishing object and used for polishing
the polishing object and a concentrate (stock solution of polishing liquid) which
is diluted for use as a polishing liquid. Other examples of the polishing liquid comprising
the polishing composition disclosed herein include a polishing liquid obtained by
adjusting the pH of the composition.
[0085] The abrasive content in the polishing liquid is not particularly limited. It is typically
0.01 % by mass or higher, preferably 0.05 % by mass or higher, or more preferably
0.1 % by mass or higher, for instance, 0.15 % by mass or higher. With increasing abrasive
content, a higher polishing rate can be obtained. From the standpoint of obtaining
a surface with lower haze, usually, the abrasive content is suitably 10 % by mass
or lower, preferably 7 % by mass or lower, more preferably 5 % by mass or lower, or
yet more preferably 2 % by mass or lower, for instance, 1 % by mass or lower.
[0086] The water-soluble polymer content in the polishing liquid is not particularly limited.
For instance, it can be 1 × 10
4 % by mass or higher. From the standpoint of haze reduction, the polymer content is
preferably 5 × 10
-4 % by mass or higher, or more preferably 1 × 10
-3 % by mass or higher, for instance, 2 × 10
-3 % by mass or higher. From the standpoint of the likelihood of forming grains in preferable
sizes disclosed herein, the polymer content is preferably 0.2 % by mass or lower,
or more preferably 0.1 % by mass or lower (e.g. 0.05 % by mass or lower).
[0087] When a surfactant is used, the surfactant content in the polishing liquid is not
particularly limited. It is usually suitable that the surfactant content is 1 × 10
-5 % by mass or higher (e.g. 1 × 10
-4 % by mass or higher). From the standpoint of haze reduction, a preferable surfactant
content is 5 × 10
-5 % by mass or higher (e.g. 5 × 10
-4 % by mass or higher), or more preferably 1 × 10
-3 % by mass or higher, for instance, 2 × 10
-3 % by mass or higher. From the standpoint of the washability, polishing rate, the
surfactant content is preferably 0.2 % by mass or lower, or more preferably 0.1 %
by mass or lower (e.g. 0.05 % by mass or lower).
[0088] When a basic compound is used, the basic compound content in the polishing liquid
is not particularly limited. From the standpoint of increasing the polishing rate,
usually, the basic compound content is preferably 0.001 % by mass or more of the polishing
liquid, or more preferably 0.005 % by mass or more. From the standpoint of haze reduction,
the basic compound content is preferably below 0.4 % by mass, or more preferably below
0.25 % by mass.
[0089] The pH of the polishing liquid is 9.0 to 11.0. It is preferable that the basic compound
is contained to yield such a pH of the polishing liquid. The above-described pH can
be preferably applied to a polishing liquid (e.g. polishing liquid for final polishing)
used for polishing a silicon wafer.
< Grains in polishing composition >
[0090] The polishing composition disclosed herein may comprise, as grains, simple abrasive
grains or grains formed by adhesion of the abrasive and water-soluble polymer. The
grain may be, for instance, in a form of an abrasive grain or a single abrasive grain
bearing one or several polymer molecules on the surface thereof, in a form of a single
polymer molecule bearing two or more abrasive grains adhered to the surface thereof,
in a form of two or more abrasive grains adhered to two or more polymer molecules,
in a form of the abrasive and water-soluble polymer further bearing other components)
(e.g. surfactant) of the polishing composition, and so on. Generally, in the polishing
composition used for polishing a polishing object, grains in several forms as exemplified
above are thought to be present as a mixture. The presence of grains formed by adhesion
of the abrasive and water-soluble polymer in the polishing composition can be detected
when the average particle diameter measured for the grains in the polishing composition
is larger than the average particle diameter of the abrasive grain.
[0091] The sizes of grains in the polishing liquid (working slurry) supplied to a polishing
object can be determined, for instance, by conducting particle size analysis based
on dynamic light scattering, using a measurement sample of the polishing liquid. The
particle size analysis can be performed, for instance, using model "UPA-UT151" available
from Nikkiso Co., Ltd. According to the studies by the present inventors, by using
a polishing liquid for which the particle size analysis yields a volume average particle
diameter D
A of a prescribed value or smaller (specifically 60 nm or smaller), as compared with
an embodiment using a polishing liquid with a larger D
A, the number of micro defects (e.g. the number of micro defects detected by the micro
defect inspection described later in the working examples) can be significantly reduced.
[0092] The lower limit of volume average particle diameter D
A is not particularly limited from the standpoint of reducing the number of micro defects.
From the standpoint of the effects of polishing (e.g. effects such as reduced haze,
removal of defects), the D
A is suitably 20 nm or larger, or preferably 30 nm or larger. From the standpoint of
balancing micro defect reduction and effects of polishing at a higher level, the D
A is preferably 35 nm or larger, more preferably 40 nm or larger, or yet more preferably
45 nm or larger. In a preferable embodiment of the art disclosed herein, the D
A can be 50 nm or larger (typically larger than 50 nm). A polishing liquid that satisfies
such a D
A may efficiently bring about a polished surface that has achieved particularly high
levels of reduction of both micro defects and haze.
[0093] The volume average particle diameter D
A can be adjusted to a desirable numerical range, for instance, by the selection of
an abrasive (sizes (D
P1, D
P2), shape, or size distribution); selection of a water-soluble polymer (composition,
Mw, Mw/Mn, or molecular structure); amount of the water-soluble polymer used relative
to the abrasive; use/non-use of a surfactant as well as selection of the type and
amount, when used. The same applies to the particle size distribution of the grains
described later.
[0094] The D
A can be measured, as described above, with the measurement sample being the polishing
composition at a concentration actually employed when supplying it to a polishing
object. In general, even if the NV is varied in a range of about 0.05 to 5 % by mass
while keeping the ratio of the respective components constant, the D
A value will not change greatly. Thus, practically, when the D
A value measured at a concentration equivalent to 0.2 % (by mass) abrasive content
(i.e. the D
A value obtained, using the polishing composition at the aforementioned concentration
as the measurement sample) is in the range, the aforementioned effects can be attained
not only when using the polishing composition as a polishing liquid at 0.2 % (by mass)
abrasive content, but also when using the polishing composition at a different abrasive
content (e.g. in the range between about 0.05 and 5 % by mass, but different from
0.2 % by mass).
[0095] It is desirable that the pH of the measurement sample is not significantly different
from the pH of the actual polishing composition (polishing liquid) supplied to a polishing
object. For instance, D
A is preferably measured for a measurement sample at pH 9.0 to 11.0, typically about
pH 10.0 to 10.5. The pH range can be preferably applied to, for instance, a polishing
composition for use in final polishing of silicon wafers.
[0096] To practice the art disclosed herein, it is unnecessary to reveal how satisfying
the D
A solves the aforementioned problem. However, it may be considered as follows: In particular,
larger grains (which can be the abrasive alone, abrasive with surrounding water-soluble
polymer adhered thereto, abrasive/water-soluble polymer assemblies) in the polishing
composition cause greater damage to the surface being polished, leading to a tendency
for the occurrence of defects. The presence of rough grains may lead to uneven polishing,
impairing the surface smoothness. Moreover, since rough grains have many points in
contact or proximity with the surface of the polishing object (i.e. areas readily
available for interactions between the two), they tend to stay on the polishing object's
surface for a long time and are likely to remain on the polished surface after completion
of the polishing. The remaining grains can be washed off. However, from the start
of wash to the elimination of grains, on the polished surface, grain-bearing areas
are less susceptible than the other areas to etching by the wash solution and thus
remain as higher areas (protrusions) than the surrounding areas on the washed surface.
These can be detected as micro defects (PID).
[0097] According to the art disclosed herein, by limiting the grain size of the polishing
liquid to not become excessively large based on the volume average particle diameter
D
A, fewer grains remain on the polished surface or remaining grains are likely eliminated
in an earlier stage of the wash (thus while there is no significant difference in
the etched amount when compared with the surroundings). This is thought to contribute
to reduce micro defects. In particular, from the standpoint of reducing the haze,
an abrasive (e.g. an abrasive having an average primary particle diameter D
P1 of smaller than 35 µm (particularly 30 nm or smaller) or an average secondary particle
diameter D
P2 of 65 µm or smaller (particularly 60 µm or smaller)) that is size-wise smaller than
a conventional general abrasive can be more advantageous than an abrasive of a conventional
size, but the behavior of abrasive grains in the polishing liquid are prone to the
influence of the water-soluble polymer adhered to the grains. Thus, it is particularly
meaningful to limit the grain size by applying the art disclosed herein.
[0098] The relationship between the volume average particle diameter D
A of the grains in the polishing composition and the abrasive's average secondary particle
diameter D
P2 theoretically satisfies D
A/D
P2 ≥ 1 and is typically D
A/D
P2 > 1. From the standpoint of greater reduction of micro defects, D
A/D
P2 is preferably 2.00 or less, more preferably 1.50 or less, or yet more preferably
1.30 or less.
[0099] The relationship between the volume average particle diameter D
A of the grains in the polishing composition and the abrasive's average primary particle
diameter D
P1 theoretically satisfies D
A/D
P1 ≥ 1 and is typically D
A/D
P1 > 1. Although not particularly limited, from the standpoint of haze reduction, D
A/D
P1 is preferably 1.30 or higher, or more preferably 1.50 or higher. From the standpoint
of haze reduction, D
A/D
P1 is preferably 5.00 or lower, more preferably 3.00 or lower, or yet more preferably
2.50 or lower.
[0100] Although not particularly limited, with respect to the polishing composition, in
the volume-based size distribution of the grains determined by dynamic light scattering
at a concentration equivalent to 0.2 % (by mass) abrasive content, the ratio (D95/D50)
of 95th percentile diameter D95 to 50th percentile diameter D50 is preferably 3.00
or lower, or more preferably 2.00 or lower (e.g. 1.80 or lower). Because there are
fewer rough grains, such a composition causes fewer defects. Since the grain size
distribution is narrow, there is little variation in the washability of the grains
remaining on the polished surface. Thus, without making the wash conditions extremely
harsh, the residue on the surface can be washed off more precisely. This can bring
about a surface of higher quality. The lower limit of D95/D50 is theoretically 1.
From the standpoint of the dispersion stability and ease of preparation of the polishing
composition, D95/D50 is suitably 1.20 or higher, preferably 1.30 or higher, or more
preferably 1.40 or higher (e.g. 1.45 or higher).
[0101] Although not particularly limited, the polishing composition disclosed herein can
be preferably made in an embodiment where the grains has a ratio of D95 (95th percentile
diameter) to D10 (10th percentile diameter), D95/D10, of 4.00 or lower. D95/D10 is
preferably 3.00 or lower, or more preferably 2.50 or lower. The lower limit of D95/D
10 is theoretically 1. From the standpoint of the dispersion stability and ease of
preparation of the polishing composition, D95/D 10 is suitably 1.50 or higher, or
preferably 1.80 or higher (e.g. 2.00 or higher).
[0102] There are no particular limitations to each of D50, D95 and D10 of the grains in
the polishing composition as far as they can bring about a preferable size distribution
disclosed herein. It is noted that D10, D50 and D95 are theoretically in a relationship
of D10 ≤ D50 ≤ D95.
[0103] From the standpoint of the polishing rate, D50 is preferably larger than 10 nm, or
more preferably larger than 20 nm. From the standpoint of obtaining greater polishing
effects, D50 is preferably 30 nm or larger, or more preferably 35 nm or larger. From
the standpoint of the likelihood of achieving a smoother surface (e.g. surface with
lower haze), D50 is suitably 90 nm or smaller, preferably 80 nm or smaller, or more
preferably 70 nm or smaller.
[0104] From the standpoint of the polishing rate, D95 is preferably 50 nm or larger, or
more preferably 60 nm or larger (e.g. 65 nm or larger). From the standpoint of reducing
scratches, D95 is suitably 120 nm or smaller, preferably 110 nm or smaller, or more
preferably 100 nm or smaller.
[0105] D10 is typically 10 nm or larger. From the standpoint of the efficiency of polishing,
it is suitably 20 nm or larger. From the standpoint of the ease of preparation of
the polishing composition, D10 is suitably smaller than 60 nm, or preferably smaller
than 50 nm.
[0106] Although not particularly limited, the polishing composition disclosed herein can
be preferably made in an embodiment where the difference between the volume average
particle diameter D
A of the grains and the abrasive's average secondary particle diameter D
P2 is 20 nm or less. More preferably, D
A-D
P2 (i.e. the value of D
A minus D
P2) is 15 nm or less (typically 0 to 15 nm). A polishing composition with a small D
A-D
P2 (i.e. with no excessive change in volume average particle diameter due to adhesion
of the abrasive and water-soluble polymer) is preferable since it tends to have a
smaller presence of rough grains. Such a polishing composition can bring about a polished
surface of higher quality.
[0107] Although not particularly limited, in the polishing composition disclosed herein,
the ratio (D
A/D50) of volume average particle diameter D
A to 50th percentile diameter D50 of the grains is preferably 1.40 or lower (e.g. 1.20
or lower). A polishing composition with a small value of the ratio (D
A/D50) is preferable because it has fewer rough grains. The lower limit of D
A/D50 is theoretically 1.
[0108] < Preparation of polishing composition >
[0109] The polishing composition disclosed herein can be produced by a suitable method that
allows formation of a polishing composition that satisfies the desirable D
A. For instance, the respective components of the polishing composition can be mixed,
using a commonly known mixing device such as a propeller stirrer, ultrasonic disperser,
homo mixer. The way of mixing these components is not particularly limited. For instance,
all the components can be mixed at once or in a suitably selected order.
[0110] Although not particularly limited, from the standpoint of the consistent (reproducible)
production of polishing compositions satisfying desirable D
A values, for instance, the following production method can be preferably employed
for the basic compound-containing polishing composition.
[0111] The polishing composition production method disclosed herein can be preferably applied
for producing a polishing composition (as its target product) comprising an abrasive,
a water-soluble polymer, a basic compound and water, wherein the polishing composition
comprising the abrasive, aggregates formed of the abrasive and water-soluble polymer
as grains, wherein the grains have a volume average particle diameter D
A of 20 nm to 60 nm when measured by dynamic light scattering at a concentration equivalent
to 0.2 % (by mass) abrasive content. In the production method, a dispersion comprising
an abrasive (e.g. silica grains), a basic compound and water (or "basic abrasive dispersion"
hereinafter) is obtained and the basic abrasive dispersion and a water-soluble polymer
are mixed.
[0112] In such a basic abrasive dispersion containing both the abrasive and basic compound,
the abrasive exhibits greater electrostatic repulsion due to the basic compound and
thus shows higher dispersion stability than an abrasive dispersion free of a basic
compound (which is typically almost neutral). Accordingly, local aggregation of the
abrasive is less likely to occur as compared with an embodiment where the basic compound
is added after addition of the water-soluble polymer to a neutral abrasive dispersion
and an embodiment where the neutral abrasive dispersion, water-soluble polymer and
basic compound are mixed all at once. Thus, according to the method where the water-soluble
polymer is mixed in the basic abrasive dispersion, adhesion of the abrasive and water-soluble
polymer is allowed to develop evenly, allowing for consistent (reproducible) production
of polishing compositions satisfying desirable D
A values.
[0113] The water-soluble polymer is preferably pre-dissolved in water and mixed in the
form of an aqueous solution (or "aqueous polymer solution" hereinafter) with the basic
abrasive dispersion. This can better inhibit local aggregation of the abrasive, whereby
adhesion of the abrasive and water-soluble polymer is allowed to develop more evenly.
[0114] When mixing the basic abrasive dispersion and aqueous polymer solution, it is preferable
to add the aqueous polymer solution to the basic abrasive dispersion. According to
such a mixing method, adhesion of the abrasive and water-soluble polymer is allowed
to develop more evenly, for instance, as compared with a mixing method where the basic
abrasive dispersion is added to the aqueous polymer solution. When the abrasive is
silica grains (e.g. colloidal silica grains), it is particularly meaningful to use
the mixing method by which an aqueous polymer solution is added to a basic abrasive
dispersion as described above.
[0115] Among the abrasive, water-soluble polymer, basic compound and water forming the polishing
composition to be produced, the basic abrasive dispersion comprises at least some
of the abrasive, at least some of the basic compound and at least some of the water.
For instance, in a preferable embodiment, the abrasive dispersion comprises all the
abrasive forming the polishing composition, at least some of the basic compound and
at least some of the water.
[0116] The basic compound content in the basic abrasive dispersion is preferably 0.01 %
by mass or greater, more preferably 0.05 % by mass or greater, or yet more preferably
0.1 % by mass or greater. With increasing basic compound content, there is a tendency
for greater inhibition of the occurrence of local aggregation during preparation of
the polishing composition. The basic compound content in the basic abrasive dispersion
is preferably 10 % by mass or less, more preferably 5 % by mass or less, or yet more
preferably 3 % by mass or less. A lower basic compound content facilitates adjustment
of the basic compound content in the polishing composition.
[0117] The basic abrasive dispersion has a pH of preferably 8 or higher, or more preferably
9 or higher. With increasing pH, there is a tendency for greater inhibition of the
occurrence of local aggregation when the water-soluble polymer or an aqueous solution
thereof is added to the basic abrasive dispersion. Thus, it allows adhesion of the
abrasive and water-soluble polymer to develop more evenly, leading to more consistent
production of polishing compositions satisfying the desirable D
A. The pH of the basic abrasive dispersion is preferably 12 or lower, more preferably
11.5 or lower, or yet more preferably 10.5 or lower. With the pH of the basic abrasive
dispersion being lower in the basic range, the amount of the basic compound required
for preparing the dispersion is reduced, making it easier to adjust the basic compound
content in the polishing composition. For instance, when the abrasive is silica grains,
it is advantageous that the pH is not excessively high also from the standpoint of
reducing dissolution of the silica. The mixture's pH can be adjusted by modifying
the amount of the basic compound added.
[0118] Such a basic abrasive dispersion can be prepared by mixing an abrasive, a basic compound
and water. They can be mixed with a commonly known mixing device such as a propeller
stirrer, ultrasonic disperser, homo mixer. The mode of mixing the respective components
of the basic abrasive dispersion is not particularly limited. For instance, the components
can be mixed all at once or in a suitably selected order. An example of preferable
embodiments is an embodiment where an approximately neutral dispersion comprising
the abrasive and water is mixed with the basic compound or an aqueous solution thereof.
[0119] When mixing the water-soluble polymer in a form of an aqueous solution (aqueous polymer
solution) into a basic abrasive dispersion, the water-soluble polymer content in the
aqueous polymer solution is preferably 0.02 % by mass or greater, more preferably
0.05 % by mass or greater, or yet more preferably 0.1 % by mass or greater. With increasing
water-soluble polymer content, it becomes easier to adjust the water-soluble polymer
content in the polishing composition. The water-soluble polymer content in the aqueous
polymer solution is preferably 10 % by mass or less, more preferably 5 % by mass or
less, or yet more preferably 3 % by mass or less. With decreasing water-soluble polymer
content, local aggregation of the abrasive tends to be more likely reduced when mixing
the aqueous polymer solution with the basic abrasive dispersion.
[0120] The pH of the aqueous polymer solution is adjusted preferably to around neutral to
basic, or more preferably to basic. More specifically, the pH of the aqueous polymer
solution is preferably 8 or higher, or more preferably 9 or higher. The pH can be
adjusted by using some of the basic compound forming the polishing composition. The
increased pH of the aqueous polymer solution can more greatly reduce local aggregation
of the abrasive when the aqueous polymer solution is added to the basic abrasive dispersion.
This allows adhesion of the abrasive and water-soluble polymer to develop more evenly,
leading to more consistent production of polishing compositions satisfying the desirable
D
A. The pH of the aqueous polymer solution is preferably 12 or lower, or more preferably
10.5 or lower. When the pH of the aqueous polymer solution is lower in the basic range,
the amount of the basic compound required for preparing the aqueous polymer solution
is reduced, making it easier to adjust the basic compound content in the polishing
composition. For instance, when the abrasive is silica grains, it is advantageous
that the pH is not excessively high also from the standpoint of reducing dissolution
of the silica.
[0121] The rate of adding the aqueous polymer solution to the basic abrasive dispersion
(supply rate) is preferably, with respect to 1 L of the dispersion, at or below 500
mL of aqueous polymer solution per minute, more preferably at or below 100 mL/min,
or yet more preferably at or below 50 mL/min. With decreasing supply rate, local aggregation
of the abrasive can be more greatly reduced.
[0122] In a preferable embodiment, the aqueous polymer solution can be filtered before added
to the basic abrasive dispersion. By filtering the aqueous polymer solution, the amounts
of contaminants and aggregates in the aqueous polymer solution can be reduced. This
allows adhesion of the abrasive and water-soluble polymer to develop more evenly,
leading to more consistent production of polishing compositions satisfying the desirable
D
A.
[0123] The filtration method is not particularly limited. Known filtration methods can be
suitably employed such as natural filtration performed at normal pressure as well
as suction filtration, pressure filtration, centrifugal filtration. The filter used
for filtration is preferably selected based on mesh size. From the standpoint of the
productivity of polishing compositions, the filter's mesh size is preferably 0.05
µm or larger, more preferably 0.1 µm or larger, or yet more preferably 0.2 µm or larger.
From the standpoint of increasing the effect of eliminating contaminants and aggregates,
the filter's mesh size is preferably 100 µm or smaller, more preferably 70 µm or smaller,
or yet more preferably 50 µm or smaller. The filter's material or construction is
not particularly limited. Examples of the filter's material include cellulose, nylon,
polysulfone, polyether sulfone, polypropylene, polytetrafluoroethylene (PTFE), polycarbonate,
glass. Examples of the filter's construction include depth, pleated, membrane.
[0124] The polishing composition production method described above can be applied when the
polishing composition obtainable by mixing the basic abrasive dispersion and the water-soluble
polymer or an aqueous solution thereof is a polishing liquid (working slurry) or has
approximately the same NV as this as well as when it is a concentrate described later.
Even when the basic abrasive dispersion and the water-soluble polymer or an aqueous
solution thereof are mixed to obtain a concentrate and the concentrate is diluted
to prepare a polishing liquid, by applying the aforementioned procedure in preparing
the concentrate (i.e. the procedure of first obtaining the basic abrasive dispersion
comprising the abrasive and basic compound and then mixing therewith the water-soluble
polymer or an aqueous solution thereof), adhesion of the abrasive and water-soluble
polymer are allowed to develop evenly. By diluting the concentrate thus prepared,
it is possible to consistently (reproducibly) produce polishing liquids satisfying
the desirable D
A.
< Polishing >
[0125] The polishing composition disclosed herein can be preferably used for polishing a
polishing object, for instance, in an embodiment comprising operations described below.
A preferable embodiment of the method for polishing a polishing object using a polishing
composition disclosed herein is described below.
[0126] In particular, a polishing slurry comprising a polishing composition disclosed herein
is obtained. As described above, obtaining the polishing slurry may comprise preparing
a polishing slurry by subjecting the polishing composition to concentration adjustment
(e.g. dilution), pH adjustment and so on. Alternatively, a polishing composition may
be used as is as the polishing slurry.
[0127] Subsequently, the polishing slurry is supplied to a polishing object and polishing
is carried out by a conventional method. For instance, when carrying out final polishing
of a silicon wafer, the silicon wafer after a lapping step and first polishing step
is set in a general polishing machine and via a polishing pad in the polishing machine,
the polishing slurry is supplied to the surface (surface to be polished) of the silicon
wafer. Typically, while the polishing slurry is continuously supplied, the polishing
pad is pushed against the surface of the silicon wafer, and the two are moved (e.g.
moved in circular motion) in coordination. Via such a polishing step, polishing of
the polishing object is completed.
[0128] A polishing step such as the above may be part of production processes of polished
articles (e.g. substrates such as silicon wafers). Accordingly, this specification
provides a method for producing a polished article (preferably, a method for producing
a silicon wafer), with the method comprising the polishing step.
[0129] In a preferable embodiment of the polished article production method disclosed herein,
as the polishing liquid supplied to the polishing object in the polishing step, it
can be preferable to use a polishing liquid comprising an abrasive, a water-soluble
polymer and water, having a volume average particle diameter D
A of grains (such as the abrasive and aggregates formed of the abrasive and the water-soluble
polymer) of 20 nm to 60 nm when measured by dynamic light scattering. The abrasive
content in the polishing liquid is not particularly limited and can be, for instance,
about 0.05 % by mass to 5 % by mass. In other words, the polished article production
method disclosed herein can be preferably practiced in an embodiment where the volume
average particle diameter D
A measured for the polishing liquid to be actually supplied to a polishing object is
within the range given above. According to such an embodiment, a polished article
(e.g. silicon wafer) can be produced with particularly effectively reduced occurrence
of micro defects.
[0130] The polishing pad(s) used in the polishing step using a polishing liquid comprising
the polishing composition disclosed herein are not particularly limited. For instance,
any of the non-woven fabric type, suede type, abrasive-bearing type, abrasive-free
type, can be used.
< Wash >
[0131] The polishing object polished with the polishing composition disclosed herein is
typically washed after polished. The wash can be carried out, using a suitable wash
solution. The wash solution used is not particularly limited. Usable examples include
SC-1 wash solution (a mixture of ammonium hydroxide (NH
4OH), hydrogen peroxide (H
2O
2) and water (H
2O); washing with SC-1 wash solution is referred to as "SC-1 washing" hereinafter),
SC-2 wash solution (a mixture of HCl, H
2O
2 and H
2O) generally used in the field of semiconductors. The temperature of the wash solution
can be, for instance, room temperature to about 90 °C. From the standpoint of increasing
the washing efficiency, a wash solution at about 50 °C to 85 °C can be preferably
used.
< Concentrate >
[0132] The polishing composition disclosed herein may be in a concentrated form (i.e. in
a form of a concentrate of the polishing liquid) before supplied to a polishing object.
The polishing composition in a concentrated form as this is advantageous from the
standpoint of the convenience and cost reduction for production, distribution, storage.
The concentration can be, for instance, about 2-fold to 100-fold by volume while it
is usually suitably about 5-fold to 50-fold. The concentration of the polishing composition
according to a preferable embodiment is 10-fold to 30-fold, for instance, 15-fold
to 25-fold.
[0133] The polishing composition in a concentrate form as this can be used in an embodiment
where it is diluted whenever desired to prepare a polishing liquid and the polishing
liquid is supplied to a polishing object. The dilution can be carried out typically
by adding and mixing an aforementioned aqueous solvent with the concentrate. When
the aqueous solvent is a solvent mixture, the dilution can be performed by adding
just some of the components of the aqueous solvent or by adding a solvent mixture
comprising the components at a mass ratio different from that of the aqueous solvent.
[0134] The concentrate can have an NV of, for instance, 50 % by mass or lower. From the
standpoint of the stability (e.g. dispersion stability of the abrasive) and ease of
filtration of the polishing composition, usually, the concentrate has an NV of suitably
40 % by mass or lower, preferably 30 % by mass or lower, or yet more preferably 20
% by mass or lower, for instance, 15 % by mass or lower. From the standpoint of the
convenience and cost reduction for production, distribution, storage and so on, the
NV of the concentrate is suitably 0.5 % by mass or higher, preferably 1 % by mass
or higher, or more preferably 3 % by mass or higher, for instance, 5 % by mass or
higher.
[0135] The abrasive content in the concentrate can be, for instance, 50 % by mass or lower.
From the standpoint of the stability (e.g. dispersion stability of the abrasive) and
ease of filtration of the polishing composition, usually, the abrasive content is
preferably 45 % by mass or lower, or more preferably 40 % by mass or lower. In a preferable
embodiment, the abrasive content can be 30 % by mass or lower, or even 20 % by mass
or lower (e.g. 15 % by mass or lower). From the standpoint of the convenience and
cost reduction for production, distribution, storage and so on, the abrasive content
can be, for instance, 0.5 % by mass or higher, preferably 1 % by mass or higher, or
more preferably 3 % by mass or higher (e.g. 5 % by mass or higher).
[0136] The water-soluble polymer content in the concentrate can be, for instance, 3 % by
mass or lower. From the standpoint of the ease of filtration and washability of the
polishing composition, usually, the water-soluble polymer content is preferably 1
% by mass or lower, or more preferably 0.5 % by mass or lower. From the standpoint
of the convenience and cost reduction for production, distribution, storage and so
on, the water-soluble polymer content is usually suitably 1 × 10
-3 or higher, preferably 5 × 10
-3 or higher, or more preferably 1 × 10
-2 or higher.
[0137] The polishing composition disclosed herein may be of a one-pack type or a multiple-pack
type such as two-pack types. For example, it may be formulated such that liquid A
including some of the components (typically, some of the components other than the
aqueous solvent) of the polishing composition and liquid B including other components
are mixed and the mixture is used for polishing of a polishing object. The art disclosed
herein can be preferably implemented in an embodiment of, for instance, a one-pack
type polishing composition.
[0138] Several worked examples relating to the present invention are described below. In
the description below, "parts" and "%" are based on mass unless otherwise specified.
< Preparation of polishing compositions >
(Example 1)
[0139] Was obtained a colloidal silica dispersion containing 20 % colloidal silica as the
abrasive and adjusted to pH 9.0 by adding ammonia water containing 29 % ammonia (NH
3) as the basic compound. The colloidal silica had an average primary particle diameter
of 23 nm and an average secondary particle diameter of 45 nm. The average primary
particle diameter was measured with a surface area analyzer under trade name "FLOW
SORB II 2300" available from Micromeritics Instrument Corporation. The average secondary
particle diameter is the volume average secondary particle diameter measured for the
colloidal silica dispersion as the measurement sample, using model "UPA-UT151" available
from Nikkiso Co., Ltd. (The same applies to the examples below).
[0140] To the colloidal silica dispersion, ammonia water was further added to prepare a
basic dispersion at pH 10.3. Was obtained an aqueous polymer solution containing 1.5
% hydroxyethyl cellulose (Mw 25 × 10
4; or "HEC-A" hereinafter) and adjusted to pH 9.0 with ammonia. The aqueous polymer
solution was added and mixed into the basic dispersion. Ultrapure water was further
added to prepare a polishing composition concentrate with 3.5 % abrasive content.
The concentrate was diluted with ultrapure water to 0.2 % abrasive content to prepare
a polishing liquid having the composition shown in Table 1. The amounts of water-soluble
polymer and ammonia water used were adjusted so that the polishing liquid had 0.010
% water-soluble polymer and 0.005 % ammonia (5 parts and 2.5 parts, respectively,
to 100 parts of abrasive). The resulting polishing liquid had a pH of 10.1.
[0141] The polishing liquid (0.2 % abrasive content) thus obtained was subjected as a measurement
sample to particle size analysis based on dynamic light scattering, using model "URA-UT151"
available from Nikkiso Co., Ltd. As a result, the grains in the measurement sample
were found to have a volume average particle diameter D
A of 56 nm. Table 1 shows the composition of the polishing liquid as well as the measured
values of the abrasive's average primary and secondary particle diameters D
P1 and D
P2 and the volume average particle diameter D
A of the grains in the measurement sample (The same applies to the examples below).
(Example 2)
[0142] In place of the aqueous polymer solution in Example 1, were used an aqueous polymer
solution containing 1.5 % HEC-A and adjusted to pH 9.0 with ammonia and an aqueous
surfactant solution. As the surfactant, a PEO-PPO-PEO block copolymer (Mw 9000) was
used. The amount used was adjusted to 0.001 % of the polishing liquid (0.5 part to
100 parts of abrasive). Otherwise, in the same manner as Example 1, was prepared a
polishing liquid having the composition shown in Table 1. Measured in the same manner
as Example 1, the grains had a volume average particle diameter D
A of 57 nm.
(Example 3)
[0143] The HEC-A concentration in the aqueous polymer solution used was changed to 0.5 times
that in Example 2. Otherwise, in the same manner as Example 2, was prepared a polishing
liquid having the composition shown in Table 1. Measured in the same manner as Example
1, the grains had a volume average particle diameter D
A of 57 nm.
(Example 4)
[0144] The HEC-A concentration in the aqueous polymer solution used was changed to 1.5 times
that in Example 2. Otherwise, in the same manner as Example 2, was prepared a polishing
liquid having the composition shown in Table 1. Measured in the same manner as Example
1, the grains had a volume average particle diameter D
A of 58 nm.
(Example 5)
[0145] Was used an aqueous polymer solution containing 2 % polyvinyl alcohol (Mw 1.3 × 10
4, degree of saponification ≥ 95 % by mole; or "PVA-1" hereinafter) in place of HEC-A
in Example 2. Otherwise, in the same manner as Example 2, was prepared a polishing
liquid having the composition shown in Table 1. Measured in the same manner as Example
1, the grains had a volume average particle diameter D
A of 46 nm.
(Comparative Example 1)
[0146] To a pH 9.0 colloidal silica dispersion containing 20 % colloidal silica (35 nm average
primary particle diameter, 66 nm average secondary particle diameter) as the abrasive,
was added ammonia water containing 29 % ammonia (NH
3) as the basic compound to prepare a basic dispersion at pH 10.3. Was obtained an
aqueous polymer solution containing 1.5 % HEC-A and adjusted to pH 9.0 with ammonia.
The aqueous polymer solution was added and mixed into the basic dispersion. Ultrapure
water was further added to prepare a polishing composition concentrate with 9.2 %
abrasive content. The concentrate was diluted with ultrapure water to 0.5 % abrasive
content to prepare a polishing liquid having the composition shown in Table 1. The
amounts of the water-soluble polymer and ammonia water used were adjusted so that
the water-soluble polymer and ammonia contents per unit surface area of abrasive per
unit volume of polishing liquid were approximately the same as those in the polishing
liquid of Example 1. Specifically, their amounts were adjusted so that their contents
(concentrations) in the polishing liquid were 0.020 % and 0.010 %, respectively.
[0147] The polishing liquid was further diluted with ultrapure water to 0.2 % abrasive content.
This was subjected as a measurement sample to particle size analysis based on dynamic
light scattering, using model "UPA-UT151" available from Nikkiso Co., Ltd. As a result,
the grains in the measurement sample were found to have a volume average particle
diameter D
A of 80 nm.
(Comparative Example 2)
[0148] In place of the aqueous polymer solution in Comparative Example 1, were used an aqueous
polymer solution containing 1.5 % HEC-Aand adjusted to pH 9.0 with ammonia and an
aqueous surfactant solution. As the surfactant, a PEO-PPO-PEO block copolymer (Mw
9000) was used in an amount equivalent to 0.002 % of the polishing liquid. Otherwise,
in the same manner as Comparative Example 1, a polishing liquid having the composition
shown in Table 1 was prepared. Measured in the same manner as Comparative Example
1, the grains had a volume average particle diameter D
A of 72 nm.
(Comparative Example 3)
[0149] To a pH 9.0 colloidal silica dispersion containing 20 % colloidal silica (12 nm average
primary particle diameter, 28 nm average secondary particle diameter) as the abrasive,
was added ammonia water containing 29 % ammonia (NH
3) as the basic compound to prepare a basic dispersion at pH 10.3. To this basic dispersion,
were added a pH 7.0 aqueous polymer solution containing 1 % hydroxyethyl cellulose
with Mw of 100 × 10
4 (or "HEC-B" hereinafter) and an aqueous surfactant solution. As the surfactant, a
PEO-PPO-PEO block copolymer (Mw 9000) was used. Ultrapure water was further added
to prepare a polishing composition concentrate with 3.5 % abrasive content. The concentrate
was diluted with ultrapure water to 0.2 % abrasive content to prepare a polishing
liquid having the composition shown in Table 1. Measured in the same manner as Example
1, the grains had a volume average particle diameter D
A of 65 nm.
(Comparative Example 4)
[0150] In place of HEC-A in Example 2, HEC-B was used. Otherwise, in the same manner as
Example 2, was prepared a polishing liquid having the composition shown in Table 1.
Measured in the same manner as Example 1, the grains had a volume average particle
diameter D
A of 71 nm.
(Comparative Example 5)
[0151] To a pH 9.0 colloidal silica dispersion containing 20 % colloidal silica (35 nm average
primary particle diameter, 66 nm average secondary particle diameter) as the abrasive,
was added ammonia water containing 29 % ammonia (NH
3) as the basic compound to prepare a basic dispersion at pH 10.3. To this basic dispersion,
were added a pH 7.0 aqueous polymer solution containing 1 % HEC-B and an aqueous surfactant
solution. As the surfactant, a PEO-PPO-PEO block copolymer (Mw 9000) was used. Ultrapure
water was further added to prepare a polishing composition concentrate with 9.2 %
abrasive content. The concentrate was diluted with ultrapure water to 0.5 % abrasive
content to prepare a polishing liquid having the composition shown in Table 1. Measured
in the same manner as Comparative Example 1, the grains had a volume average particle
diameter D
A of 90 nm.
(Example 6)
[0152] As the water-soluble polymer, was used a polyacryloylmorpholine with Mw of 7 × 10
4 (or "PACMO-1" hereinafter). Otherwise, in the same manner as Example 2, was prepared
a polishing liquid having the composition shown in Table 2. Measured in the same manner
as Example 1, the grains had a volume average particle diameter D
A of 48 nm.
(Example 7)
[0153] As the water-soluble polymer, was used a polyvinyl alcohol with Mw of 1.3 × 10
4 (80 % by mole vinyl alcohol unit, 20 % by mole vinyl hexanoate unit; or "PVA-2" hereinafter).
Otherwise, in the same manner as Example 2, was prepared a polishing liquid having
the composition shown in Table 2. Measured in the same manner as Example 1, the grains
had a volume average particle diameter D
A of 46 nm.
(Example 8)
[0154] As the water-soluble polymer, was used a polyvinyl alcohol with Mw of 0.5 × 10
4 (80 % by mole vinyl alcohol unit, 20 % by mole vinyl hexanoate unit; or "PVA-3" hereinafter).
Otherwise, in the same manner as Example 2, was prepared a polishing liquid having
the composition shown in Table 2. Measured in the same manner as Example 1, the grains
had a volume average particle diameter D
A of 46 nm.
(Example 9)
[0155] As the water-soluble polymer, were used PVA-3 and a polyvinylpyrrolidone with Mw
of 6 × 10
4 (PVP). Otherwise, in the same manner as Example 2, a polishing liquid having the
composition shown in Table 2 was prepared. Measured in the same manner as Example
1, the grains had a volume average particle diameter D
A of 46 nm.
(Example 10)
[0156] As the water-soluble polymer, were used HEC-A and a polyacryloylmorpholine with Mw
of 8 × 10
4 (or "PACMO-2" hereinafter). Otherwise, in the same manner as Example 2, was prepared
a polishing liquid having the composition shown in Table 2. A measurement sample adjusted
by dilution to 0.2 % abrasive content was measured in the same manner as Comparative
Example 1 and the grains were found to have a volume average particle diameter D
A of 51 nm.
(Example 11)
[0157] As the water-soluble polymer, were used HEC-A and PVP. Otherwise, in the same manner
as Example 2, was prepared a polishing liquid having the composition shown in Table
2. A measurement sample adjusted by dilution to 0.2 % abrasive content was measured
in the same manner as Comparative Example 1 and the grains were found to have a volume
average particle diameter D
A of 50 nm.
< Silicon Wafer Polishing >
[0158] Silicon wafer surfaces were polished with the polishing compositions according to
the respective examples under the conditions shown below. The silicon wafers used
had 300 mm diameter, p-type conductivity, crystal orientation of <100> and a resistivity
of 0.1 Ω·cm or greater, but less than 100 Ω·cm, and were preliminarily polished with
a polishing slurry (trade name "GLANZOX 2100" available from Fujimi Inc.) to a surface
roughness of 0.1 nm to 10 nm for the use.
[Polishing Conditions]
[0159] Polishing machine: Sheet-type polisher with model number "PNX-332B" available from
Okamoto Machine Tool Works, Ltd.
[0160] Polishing tables: Using two rear tables among three tables of the polishing machine,
the first and second stages of final polishing after the preliminary polishing were
carried out.
(The conditions below were common between the two tables)
[0161] Polishing pressure: 15kPa
Plate rotational speed: 30 rpm
Head rotational speed: 30 rpm
Polishing time: 2 min
Temperature of polishing liquid: 20 °C
Flow rate of polishing liquid: 2.0 L/min (drain)
< Wash >
[0162] Polished silicon wafers were washed (SC-1 washed) with a wash solution at NH
4OH (29%)/H
2O
2 (31%)/deionized water (DIW) = 1/3/30 (volume ratio). More specifically, two washing
baths each equipped with an ultrasonic wave oscillator of 950 kHz frequency were obtained;
the wash solution was placed in each of the first and second washing baths and maintained
at 60 °C; and each polished silicon wafer was immersed in the first washing bath for
6 minutes and then, via a ultrasonic rinsing bath with ultrapure water, in the second
washing bath for 6 minutes, with the respective ultrasonic wave oscillators turned
on.
< Micro defect Inspection >
[0163] The surfaces of the respective washed silicon wafers were inspected with a wafer
inspection system under trade name "MAGICS M5350" available from Lasertec Corporation.
Table 1 and Table 2 show the results in the five grades shown below based on the number
of micro defects detected in the silicon wafer surfaces of 300 mm diameter.
A++: micro defects detected <100
A+: micro defects detected ≥ 100, < 150
A: micro defects detected ≥ 150, < 200
B: micro defects detected ≥ 200, < 500
C: micro defects detected ≥ 500
< Haze Measurement >
[0164] The surface of the respective washed silicon wafers were measured for haze (ppm)
in DWO mode, using a wafer inspection system under trade name "SURFSCAN SP2" available
from KLA-Tencor Corporation. The measurement results are shown in the three grades
indicated below in Table 1 and Table 2.
- A: <0.10ppm
- B: ≥ 0.10 ppm, < 0.12 ppm
- C: ≥ 0.12 ppm
[Table 1]
[0165]
Table 1
|
Example |
Comparative Example |
1 |
2 |
3 |
4 |
5 |
1 |
2 |
3 |
4 |
5 |
Composition (wt%) |
Abrasive |
0.2 |
0.2 |
0.2 |
0.2 |
0.2 |
0.5 |
0.5 |
0.2 |
0.2 |
0.5 |
Water-soluble polymer |
HEC-A (Mw 25×104) |
0.010 |
0.010 |
0.005 |
0.015 |
- |
0.020 |
0.020 |
- |
- |
- |
HEC-B (Mw 100×104) |
- |
- |
- |
- |
- |
- |
- |
0.010 |
0.010 |
0.010 |
PVA -1 (Mw 13×104, deg. of saponification ≥ 95 mol%) |
- |
- |
- |
- |
0.010 |
- |
- |
- |
- |
- |
Surfactant |
- |
0.001 |
0.001 |
0.001 |
0.001 |
- |
0.002 |
0.001 |
0.001 |
0.002 |
Basic compound (NH3) |
0.005 |
0.005 |
0.005 |
0.005 |
0.005 |
0.010 |
0.010 |
0.005 |
0.005 |
0.010 |
Abrasive |
Average primary particle diameter DP1 (nm) |
23 |
24 |
24 |
24 |
24 |
35 |
35 |
12 |
23 |
35 |
Average secondary particle diameter DP2 (nm) |
45 |
46 |
46 |
46 |
46 |
66 |
66 |
28 |
45 |
66 |
Grains in composition |
Volume average particle diameter DA (nm) |
56 |
57 |
57 |
58 |
46 |
80 |
72 |
65 |
71 |
90 |
DA/DP2 |
1.24 |
1.24 |
1.24 |
1.26 |
1.00 |
1.21 |
1.09 |
2.32 |
1.58 |
1.36 |
DA/DP1 |
2.43 |
2.38 |
2.38 |
2.42 |
1.92 |
2.29 |
2.06 |
5.42 |
3.09 |
2.57 |
Test Results |
Micro defects |
A |
A+ |
A+ |
A+ |
A |
B |
B |
C |
C |
C |
Haze |
B |
A |
A |
A |
B |
C |
C |
B |
B |
B |
[Table 2]
[0166]
Table 2
|
Example |
6 |
7 |
8 |
9 |
10 |
11 |
Composition (wt%) |
Abrasive |
0.2 |
0.2 |
0.2 |
0.2 |
0.1 |
0.1 |
Water-soluble polymer |
HEC-A (Mw 25×104) |
- |
- |
- |
- |
0.005 |
0.005 |
PVA-2 (Mw 1.3×104, deg. of saponification 80 mol%) |
- |
0.003 |
- |
- |
- |
- |
PVA-3 (Mw 0.5×104, deg. of saponification 80 mol%) |
- |
- |
0.003 |
0.005 |
- |
- |
PACMO-1 (Mw 7×104) |
0.005 |
- |
- |
- |
- |
- |
PACMO-2 (Mw 8×104) |
- |
- |
- |
- |
0.003 |
- |
PVP (Mw6×104) |
- |
- |
- |
0.003 |
- |
0.003 |
Surfactant |
0.001 |
0.001 |
0.001 |
0.001 |
0.0001 |
0.0001 |
Basic compound (NH3) |
0.005 |
0.005 |
0.005 |
0.005 |
0.005 |
0.005 |
Abrasive |
Average primary particle diameter DP1 (nm) |
24 |
24 |
24 |
24 |
25 |
25 |
Average secondary particle diameter DP2 (nm) |
46 |
46 |
46 |
46 |
48 |
48 |
Grains in composition |
Volume average particle diameter DA (nm) |
48 |
46 |
46 |
46 |
51 |
50 |
DA/DP2 |
1.04 |
1.00 |
1.00 |
1.00 |
1.06 |
1.04 |
DA/DP1 |
200 |
1.92 |
1.92 |
1.92 |
2.04 |
2.00 |
Test Results |
Micro defects |
A |
A+ |
A+ |
A++ |
A++ |
A++ |
Haze |
B |
A |
A |
A |
A |
A |
[0167] As evident from Table 1, the use of the polishing liquids of Examples 1 to 5 of which
the grains in the polishing compositions had D
A values in a range of 20 nm to 60 nm (more specifically 35 nm to 60 nm) produced an
effect to singificantly reduce the number of micro defects detected when compared
with Comparative Examples 1 to 5 using polishing liquids with larger D
A values. In comparison of Examples 1 and 2, the use of the surfactant (PEO-PPO-PEO
block copolymer with Mw of 9000 herein) produced an effect to reduce the haze while
keeping the great effect to reduce micro defects. According to Examples 2 to 4, both
micro defect reduction and haze reduction were achieved at a particularly high level.
[0168] Also in Examples 6 to 11 shown in Table 2, the polishing liquids of which the grains
in the polishing compositions had D
A values in the range of 20 nm to 60 nm (more specifically 35 nm to 60 nm) were found
to produce an effect to significantly reduce the number of detectable micro defects.
[0169] On the contrary, in Comparative Examples 3 to 5 using polishing liquids with D
A values above 60 nm, while their haze levels were comparable to Examples 1 and 5,
they clearly had more micro defects detected as compared with Examples 1 to 5. With
respect to Comparative Examples 1 and 2, while they had fewer micro defects than Comparative
Examples 3 to 5, they had higher haze than Examples 1 to 5 and did not achieve both
micro defect reduction and haze reduction at a high level. It is noted that in Comparative
Examples 2 and 3, despite that their abrasive's average secondary particle diameters
were about the same as or smaller than those of Examples 1 to 5, their grains in the
polishing compositions had excessively large sizes (D
A) and the cause for this may be the large Mw of the water-soluble polymers used in
Comparative Examples 2 and 3.